7 Best InboxKit Alternatives in 2026

InboxKit is a popular cold email infrastructure platform that provides Google Workspace, Microsoft 365, and Azure mailboxes for outbound campaigns.

But as your setup grows, a few InboxKit limitations can become more noticeable:

• Costs increase as you add mailboxes and enable features per mailbox.
• Plans come with fixed mailbox slots such as 10, 30, or 100, so scaling depends on plan limits and additional mailboxes.
• Warmup and InfraGuard are not included by default and need to be enabled separately.
• You can't launch campaigns at scale immediately. Mailboxes need to be warmed up, typically for around 14 days.
• Deliverability setup is split across features such as warmup, monitoring, and inbox placement tests instead of being handled in one flow.
• Some users report slow responses when they need help with deliverability issues or mailbox problems.
• InboxKit only offers Google Workspace, Microsoft 365, and Azure mailboxes. If you need shared IP infrastructure or private infrastructure with dedicated IPs, you need another infrastructure provider.

I compared seven InboxKit alternatives based on mailbox types, pricing, warmup, email infrastructure, DNS setup, sending limits, scalability, and operational workload.

TL;DR: 7 Best InboxKit Alternatives at a Glance

• Primeforge: Best for real Google Workspace and Microsoft 365 mailboxes with pre-warmed mailboxes, automated DNS, multiple workspaces, and API, MCP, and CLI access.
• Mailforge: Best for scaling shared email infrastructure with bulk mailbox creation, bulk DNS updates, workspaces, and lower mailbox costs at higher volumes.
• Infraforge: Best for private email infrastructure and dedicated IPs with automated warmup and monitoring, multi-IP provisioning, and sender rotation.
• Zapmail: Best for pre-warmed Google Workspace and Microsoft 365 mailboxes with isolated workspaces, automated DNS configuration, and 50+ outreach tools supported.
• Icemail: Best for flexible, pay-as-you-go mailbox provisioning across Google, Microsoft 365, Azure, and private infrastructure.
• Puzzle Inbox: Best for low-cost Google Workspace inboxes and Outlook inboxes, including pre-warmed options and particularly cheap Outlook mailboxes.
• Maildoso: Best for high-volume SMTP mailboxes with proprietary infrastructure, IP rotation, and plans that become more cost-effective as your mailbox count grows.

How I Compared These InboxKit Alternatives

I compared the providers based on the parts that matter when you are buying and managing cold email infrastructure:

• How much does each provider charge for mailboxes, domains, warmup, and other required features?
• Does each provider offer Google Workspace, Microsoft 365, Azure, shared infrastructure, private infrastructure, or SMTP mailboxes?
• Can you get pre-warmed mailboxes, or do you need to warm fresh accounts before starting campaigns?
• What does each provider offer for DNS setup, email authentication, IP management, and daily sending limits?
• How easily can you manage domains and hundreds or thousands of mailboxes as your sending volume grows?
• Can you automate mailbox management through APIs, MCP, CLI, or integrations with your existing sending tools?

7 Top InboxKit Alternatives Compared at a Glance

Check this table to go through the InboxKit alternatives for a quick overview.

7 Top InboxKit Alternatives Discussed in Detail

Let's look at each cold email infrastructure provider in detail, including its features, pros, cons, and pricing.

1. Primeforge

Best for: Sales teams, outbound teams and agencies that want real Google Workspace and Microsoft 365 mailboxes with pre-warmed options, automated DNS setup, and flexible mailbox management.

Primeforge is a cold email infrastructure platform that offers real Google Workspace accounts and Microsoft 365 mailboxes for outbound campaigns. You can choose standard or pre-warmed mailboxes based on your campaign needs.

Compared with InboxKit, Primeforge includes more of the essential setup from the start. The platform automatically configures SPF, DKIM, DMARC, and tracking DNS for every domain, so domain setup is handled for you. You also get mailbox analytics, workspaces, and free domain transfers.

Primeforge supports full API access, MCP, and CLI as well. These options let you create mailboxes and manage them at scale without setting up each account manually.

The platform uses official Google Workspace and Microsoft inboxes. There are no loopholes, no EDU tricks, and no fragile infrastructure.

Mailboxes also run on different safe IP addresses, which gives you a cleaner setup for managing sender reputation and better inbox placement in cold email outreach.

Primeforge Key Features

• Use real Google Workspace and Microsoft 365 mailboxes for outbound campaigns.
• Start with pre-warmed mailboxes when you want to skip the initial warmup period.
• Match the sending provider to your prospect's mailbox provider with ESP Matching.
• Configure SPF, DKIM, and DMARC automatically for every domain.
• Set up mailbox profile pictures, GIFs, and sender profiles before starting campaigns.
• Forward secondary domains to your main website or landing page.
• Connect domains from any registrar to Primeforge for free.
• Pay only for the mailboxes created on connected domains, with no additional domain connection fees.
• Organize mailboxes across multiple workspaces for different clients and projects.
• Connect Primeforge to any sending software or use the native Salesforge integration.
• Create and manage mailboxes through the Primeforge API.
• Access mailbox management through Forge MCP CLI for scripted and agent-based workflows.

Pros

• Real Google Workspace and Microsoft 365 mailboxes.
• Pre-warmed mailbox options for faster campaign launches.
• Automated DNS setup for SPF, DKIM, and DMARC.
• API, MCP, and CLI access for automated mailbox management.
• Free domain connections with no additional domain connection fee.

Cons

• No free mailboxes are available.
• Only Google Workspace and Microsoft 365 mailboxes are available. SMTP or other mailbox types require another provider.

Primeforge Pricing

Primeforge pricing ranges from around $4.50 to $3.50 per mailbox per month, depending on your mailbox count and whether you choose annual billing or monthly billing.

Pre-warmed mailboxes are also available when you want to avoid waiting for a new mailbox to warm up.

Last but not least, domains are charged separately.

2. Mailforge

Best for: GTM teams and agencies scaling shared email infrastructure with bulk domain and bulk mailbox creation.

Mailforge is a shared email infrastructure platform for cold email campaigns. It lets you create mailboxes and manage multiple domains in bulk, which makes the setup easier when you need to scale outreach.

Compared with InboxKit, Mailforge gives you a more scalable setup at a lower mailbox cost. It includes automated SPF, DKIM, DMARC, and tracking DNS, pre-warmed domains and mailboxes, workspaces, and free domain transfers.

Mailforge also supports API, MCP, and CLI access. You can use these options to provision domains and mailboxes, manage your infrastructure, and automate repetitive setup tasks.

The shared IP setup also keeps the infrastructure cost lower than a private setup. It can be a practical option when you need more sending capacity without paying for dedicated infrastructure.

For a closer look at how it performs, read the full Mailforge review.

Mailforge Key Features

• Create shared cold email infrastructure with mailboxes distributed across a shared IP pool.
• Create hundreds or thousands of domains and mailboxes based on your sending volume.
• Set up SPF, DKIM, DMARC, and tracking DNS automatically for every domain.
• Update DNS records across multiple domains in a few clicks.
• Forward secondary domains to your main website or landing page.
• Connect domains from any registrar to Mailforge for free.
• Pay only for the mailboxes created on connected domains, with no additional domain connection fees.
• Organize domains and mailboxes by workspace and move them between workspaces when needed.
• Add SSL and domain masking to protect your primary domain and brand identity.
• Connect Mailforge with any sending software or use its native Salesforge integration.
• Manage domains and mailboxes through MCP CLI from Claude, Cursor, and other AI clients.

Pros

• Lower mailbox costs for larger sending setups.
• Bulk domain and mailbox creation saves setup time.
• Automated DNS and bulk DNS management.
• API, MCP, and CLI access for automated infrastructure management.
• Free domain connections with no additional domain connection fee.

Cons

• Only shared email infrastructure is available. Dedicated IPs, Google Workspace, and Microsoft 365 mailboxes are not offered.
• There is no free trial.

Mailforge Pricing

Mailforge starts at around $3 per mailbox per month and can fall to around $2 per mailbox at higher volumes on annual billing.

The platform uses mailbox slots, with a minimum setup requirement. Domains are priced separately based on the TLD.

SSL and domain masking are additional options.

Warmup can be handled through Warmforge with Salesforge.

3. Infraforge

Best for: Outbound teams and agencies that want private email infrastructure with dedicated IPs, automated warmup, and more control over sender reputation.

Infraforge is a private email infrastructure platform for cold email campaigns. It gives you dedicated IPs and keeps your sending infrastructure separate from shared networks.

Compared with InboxKit, Infraforge gives you more control over your sending infrastructure. It includes automated SPF, DKIM, DMARC, and tracking DNS setup. You also get automated warmup, monitoring, sender rotation, and multi-IP provisioning.

Infraforge supports full API access, MCP, and CLI. You can use these tools to provision unlimited email accounts and manage mailboxes without doing every setup task manually.

You can also choose pre-warmed infrastructure and transfer your domains for free. This makes it easier to move your existing setup and get your infrastructure ready for sending.

For a closer look at how it performs, read the full Infraforge review.

Infraforge Key Features

• Run mailboxes on private infrastructure with dedicated IPs.
• Start with pre-warmed mailboxes and domains when you want to avoid the standard two-to-four-week warmup period.
• Assign multiple dedicated IPs to separate campaigns, clients, or sending workloads.
• Create unlimited domains and mailboxes with automated SPF, DKIM, and DMARC setup.
• Generate domains and mailboxes in bulk for high-volume outreach.
• Forward secondary domains to your main website or landing page.
• Monitor mailbox deliverability in real time and receive alerts when issues arise.
• Manage replies across accounts from one Masterbox view.
• Secure domains with SSL and domain masking.
• Connect domains from any registrar to Infraforge for free.
• Pay only for the mailboxes created on connected domains, with no additional domain connection fees.
• Organize infrastructure by workspace and move domains or mailboxes between workspaces.
• Run Infraforge under your own brand with the white-label option.
• Manage domains, mailboxes, and IPs through the Infraforge API.
• Manage infrastructure through Forge MCP CLI with scripted and agent-based workflows.
• Connect Infraforge directly to Salesforge or other sending tools.

Pros

• Dedicated IP infrastructure gives you more control over sender reputation.
• Pre-warmed infrastructure helps you start campaigns sooner.
• Multi-IP setup separates campaigns and sending workloads.
• Real-time deliverability monitoring and automated warmup.
• API, MCP, and CLI access for automated infrastructure management.
• Free domain connections with no additional domain connection fee.

Cons

• There is no free trial.
• Only private infrastructure with dedicated IPs is available. Shared infrastructure, Google Workspace, and Microsoft 365 mailboxes are not offered.

Infraforge Pricing

Infraforge starts at around $4 per mailbox per month and can fall to around $3 per mailbox at higher volumes.

The subscription includes automated DNS setup and infrastructure hosting and maintenance.

Pre-warmed infrastructure is also available.

4. Zapmail

Best for: Agencies and outbound teams that want pre-warmed Google Workspace and Microsoft 365 mailboxes with isolated workspaces and broad outreach tool support.

Zapmail is a provider of Google Workspace and Microsoft 365 mailboxes for cold email campaigns. It offers standard and pre-warmed mailboxes, so you can choose fresh accounts or mailboxes that are ready for sending.

Compared with InboxKit, Zapmail adds pre-warmed mailbox options and 50+ sending tool integrations. InboxKit also offers Azure mailboxes, 24+ integrations, and built-in monitoring.

Zapmail handles the main technical setup for you. SPF, DKIM, DMARC, and tracking domains can be configured automatically. You can also bring your own domains and manage DNS and forwarding from the platform.

The platform also offers separate workspaces and API access, and connects to most outreach platform tools. Its pre-warmed mailboxes have already gone through the warmup process, so you can start campaigns without waiting for a new mailbox to warm up.

For a closer look at what users say, read the full Zapmail review.

Zapmail Key Features

• Get Google Workspace and Microsoft 365 mailboxes for cold email campaigns.
• Start with pre-warmed mailboxes when you want to avoid the initial warmup period.
• Create separate workspaces for different domains and campaigns.
• Configure SPF, DKIM, DMARC, and tracking domains automatically.
• Generate domain and mailbox names with built-in AI tools.
• Set up profile images for your mailboxes before sending.
• Connect mailboxes with more than 50 sending and outreach tools.
• Export mailboxes to platforms such as Instantly, Smartlead, Reply, and Lemlist.
• Run inbox placement tests with the credits included in your plan.

Pros

• Google Workspace and Microsoft 365 mailboxes.
• Pre-warmed mailbox options.
• Automated DNS setup.
• Support for 50+ sending and outreach tools.
• Workspace separation for different domains and campaigns.

Cons

• Fixed plans can make scaling less flexible.
• Some advanced features depend on the plan.

Zapmail Pricing

Zapmail pricing starts at:

• Starter: $39/month for 10 mailboxes.
• Growth: $99/month for 30 mailboxes.
• Pro: $299/month for 100 mailboxes.

Additional mailboxes are available on the plans at different rates.

Microsoft 365 mailboxes are priced at the same tiers as Google Workspace.

Domains are charged separately.

If Zapmail doesn't fit your setup, compare these Zapmail alternatives.

5. Icemail

Best for: Solo SDRs and small teams that want pay-as-you-go mailbox provisioning across Google, Microsoft 365, Azure mailboxes, and private infrastructure.

Icemail is a cold email infrastructure platform that supports Google Workspace, Microsoft 365, Azure, and custom IMAP/SMTP mailboxes. It also offers standard and pre-warmed mailbox options.

Compared with InboxKit, Icemail gives you more infrastructure choices, including custom IMAP/SMTP mailboxes and dedicated IP options. InboxKit focuses on Google Workspace, Microsoft 365, and Azure with built-in monitoring and API access.

Icemail handles SPF, DKIM, DMARC, and MX configuration automatically. You can connect existing domains or purchase domains through the platform and export mailboxes to external providers and supported sending tools.

The platform also supports bulk mailbox creation and mailbox replacement. Its different infrastructure options give you more flexibility when your sending setup requires something beyond standard Google or Microsoft mailboxes.

For a closer look at what users say, read the full Icemail review.

Icemail Key Features

• Get Google, Microsoft 365, Azure, and private mailboxes from one platform.
• Choose standard or pre-warmed mailboxes based on your campaign requirements.
• Pay for the number of mailboxes you need with a pay-as-you-go model.
• Configure SPF, DKIM, and DMARC automatically during setup.
• Replace failed mailboxes without paying for a replacement.
• Organize mailboxes and domains across separate workspaces.
• Connect mailboxes to your existing sending tools.
• Manage replies from multiple mailboxes through one central inbox.

Pros

• Supports Google, Microsoft 365, Azure, and private infrastructure.
• Pay-as-you-go pricing gives you more flexibility.
• Standard and pre-warmed mailbox options.
• Automated DNS setup.
• Free mailbox replacement when an account fails.

Cons

• Pre-warmed mailboxes cost more than standard mailboxes.
• Multiple infrastructure options can make setup more complex.

Icemail Pricing

Icemail standard mailboxes cost around $2.50 per mailbox per month on a pay-as-you-go basis.

Pre-warmed mailboxes cost around $5 per mailbox.

Last but not least, domains are listed at around $18 each. There is no fixed subscription requirement.

6. Puzzle Inbox

Best for: Budget-conscious teams and agencies that need low-cost Google Workspace inboxes and Outlook mailboxes.

Puzzle Inbox is a cold email infrastructure provider offering real Google Workspace and Microsoft 365 mailboxes. You can choose standard or pre-warmed inboxes based on your campaign requirements.

Compared with InboxKit, Puzzle Inbox focuses on Google Workspace and Microsoft 365 with controlled sending limits. InboxKit also offers Azure mailboxes, 24+ integrations, API access, and real-time monitoring.

Pre-warmed inboxes go through a 14-day warmup before delivery. Standard inboxes use your own domain, while Puzzle Inbox handles SPF, DKIM, and DMARC configuration for you.

Puzzle Inbox supports sending platforms such as Smartlead, Instantly, Lemlist, and Saleshandy. Its published limits are 12 cold emails per day for Google Workspace and 3 for Outlook 365, so larger campaigns require more inboxes.

For a closer look at how it performs, read the full Puzzle Inbox review.

Puzzle Inbox Key Features

• Get Google Workspace and Outlook 365 mailboxes for cold email campaigns.
• Choose standard or pre-warmed mailboxes based on your sending requirements.
• Receive mailboxes with SPF, DKIM, and DMARC already configured.
• Set up OAuth authentication for supported sending tools.
• Choose between Google Workspace and Outlook 365 mailboxes.
• Receive new mailboxes within the stated delivery timeframe.
• Start with pre-warmed accounts when you want to avoid warming fresh mailboxes yourself.

Pros

• Google Workspace and Outlook 365 mailbox options.
• Very low-cost Outlook mailbox plans.
• Pre-warmed mailbox options.
• DNS and OAuth setup reduce manual configuration.

Cons

• Daily sending limits are relatively low.
• Google inboxes have mailbox-per-domain limits.

Puzzle Inbox Pricing

Current listed pricing includes:

• Google Workspace standard: $3 per inbox/month.
• Google Workspace warmed: $4.50 per inbox/month.
• Outlook 365 standard: $0.35 per inbox/month.
• Outlook 365 warmed: $0.50 per inbox/month.

Published sending limits include:

• Google: 12 emails per inbox per day.
• Outlook: 3 emails per inbox per day.
• Google: 3 inboxes per domain.

If Puzzle Inbox doesn't fit your setup, compare these Puzzle Inbox alternatives.

7. Maildoso

Best for: High-volume senders and agencies running SMTP mailboxes with IP rotation and lower costs as the mailbox count grows.

Maildoso is an email infrastructure provider focused on SMTP-based cold email sending. It uses proprietary SMTP infrastructure and IP rotation rather than standard Google Workspace or Microsoft 365 mailboxes.

Compared with InboxKit, Maildoso uses SMTP infrastructure and IP rotation, while InboxKit provides Google Workspace, Microsoft 365, and Azure mailboxes with automated DNS, monitoring, API access, and 24+ integrations.

Maildoso is aimed at larger sending setups where SMTP infrastructure and IP management are important. It also provides mailbox and domain management features, including bounce tracking, for running multiple sending accounts.

The main difference is the infrastructure model. Maildoso gives you an SMTP-based setup, while InboxKit gives you provider-native Google, Microsoft, and Azure mailboxes.

For a closer look at how it performs, read the full Maildoso review.

Maildoso Key Features

• Run cold email campaigns on proprietary SMTP infrastructure.
• Rotate IPs across your sending infrastructure.
• Add Google Workspace mailboxes through the Combo option.
• Configure DNS for domains and mailboxes during setup.
• Get domains included with selected quarterly plans.
• Manage replies from multiple accounts through Master Inbox.
• Connect Maildoso with supported sending platforms.
• Manage your infrastructure through API and MCP access.

Pros

• Low mailbox costs at higher volumes.
• Proprietary SMTP infrastructure with IP rotation.
• Domains included with selected quarterly plans.
• API and MCP access for automated and scripted infrastructure management.

Cons

• Native warmup is not included.
• Uses SMTP infrastructure instead of native Google Workspace or Microsoft 365 mailboxes.

Maildoso Pricing

Maildoso pricing varies by plan and volume. Example quarterly plans include:

Monthly Maildoso pricing starts at $2.50 per mailbox, totaling $75 per month for 30 mailboxes, so I suggest checking the current plan before budgeting.

These plans don't include warmup.

If Maildoso doesn't fit your setup, compare these Maildoso alternatives.

How to Choose the Right Cold Email Infrastructure Provider

Before you switch, work through these points. They decide more about your results than the mailbox price does.

• Check the setup time: Pre-warmed mailboxes can help you start sooner, while fresh accounts may need two to four weeks of warmup.
• Match the mailbox type to your prospects: Choose Google Workspace or Microsoft 365 mailboxes if most of your prospects use those providers.
• Check daily sending limits: A low-cost mailbox may require more inboxes if it has a low daily sending limit.
• Calculate the real cost: Include mailboxes, domains, warmup, monitoring, and inbox placement tests.
• Look at DNS automation: Automated DNS setup and bulk updates can save time when managing multiple domains.
• Check client separation: Workspaces, separate domains, and dedicated IPs can help keep different clients and campaigns separate.
• Check automation: API, MCP, CLI, and bulk mailbox creation can reduce manual work as your mailbox count increases.
• Plan for growth: Check whether you can move from shared infrastructure to dedicated IPs as your sending volume grows.
• Ask about support: Check what level of support comes with your plan, and whether priority support, a dedicated Slack channel, or a custom plan is available at your volume.

Final Thoughts

InboxKit is one option for provisioning Google Workspace, Microsoft 365, and Azure mailboxes for cold email campaigns.

If you want more control over mailbox setup, pre-warmed options, and automated infrastructure management, Primeforge is another option to consider.

Primeforge offers real Google Workspace and Microsoft 365 mailboxes, pre-warmed options, automated DNS setup, workspaces, and API, MCP, and CLI access. You can also connect your domains for free and manage your mailbox setup from one platform.

Want to try Primeforge for your next campaign? Sign up and explore Primeforge.

FAQs About InboxKit Alternatives

1. What is the best InboxKit alternative for Google Workspace and Microsoft 365 mailboxes?

Primeforge and Zapmail both provide Google Workspace and Microsoft 365 mailboxes with pre-warmed options. Primeforge also provides API, MCP, and CLI access, while Zapmail focuses on isolated workspaces and integrations with 50+ outreach tools.

2. Is there a cheaper InboxKit alternative?

Several providers have lower starting prices depending on the email infrastructure you need. Icemail starts around $2.50 per mailbox, Mailforge starts around $3 and can fall to $2 at higher volumes, while Maildoso has lower effective rates on larger SMTP plans. The total cost depends on domains, warmup, and the rest of your setup.

3. Which InboxKit alternative offers dedicated IPs?

Infraforge provides private email infrastructure with dedicated IPs. It also supports multi-IP provisioning, automated warmup, monitoring, sender rotation, and smart sending limits, which gives you more control over sender reputation.

4. Which alternative has the cheapest Outlook mailboxes?

Puzzle Inbox lists Outlook 365 inboxes at around $0.35 per month for standard accounts and $0.50 for warmed accounts. The published sending limit is 3 emails per day per Outlook inbox, so the number of inboxes required should be considered alongside the mailbox price.

5. Are pre-warmed mailboxes available from InboxKit alternatives?

Yes. Primeforge, Zapmail, Icemail, Puzzle Inbox, and Infraforge offer pre-warmed mailbox or infrastructure options. Mailforge also has pre-warmed infrastructure options.

6. Does InboxKit include warmup?

InboxKit offers warmup as an additional feature rather than including it by default. The available pricing information lists warmup at $3 per mailbox per month, with a typical 14-day ramp for new mailboxes.

7. Which InboxKit alternative is suitable for high-volume outbound campaigns?

It depends on the infrastructure you need. Mailforge provides shared infrastructure for large mailbox setups, Infraforge provides private infrastructure with dedicated IPs and unlimited inboxes, and Maildoso provides proprietary SMTP infrastructure with IP rotation.

8. Do these providers handle DNS records for me?

Most of them do. Primeforge, Mailforge, Infraforge, Zapmail, Icemail, and Puzzle Inbox all offer automated DNS configuration covering SPF, DKIM, and DMARC, and several support bulk DNS updates across multiple domains.