kitio.aiMails.ai vs Sendmux
A side-by-side look at pricing plans, free tiers, features, pros and cons, updated for 2026. Sendmux has the lower starting price: about $7 a month, against $20 for Mails.ai.
At a glance
Best for
Pricing model
Starting price
Free plan
Made by
Based in
Rating
Key features
- Inbox per agent through one API call
- TypeScript and Python SDKs
- MCP server
- Injection scan on inbound mail
- Send from your own domain
- Agent mailboxes
- Send and receive API
- Calendar and file storage
- Hosted MCP server
- Provider failover
- SDKs and CLI
| Feature | Mails.ai | Sendmux |
|---|---|---|
| Best for | Email API that gives AI agents their own inboxes | Email, calendar and file API that gives AI agents real inboxes |
| Category | Coding | Coding |
| Pricing model | Freemium | Freemium |
| Starting price | $20/mo | $7/mo |
| Free plan | Yes | Yes |
| Made by | Mails.ai | Sendmux |
| Based in | – | – |
| Rating | No ratings yet | No ratings yet |
| Key features |
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Pricing compared
Sendmux has the lower starting price: about $7 a month, against $20 for Mails.ai.
Free plan
Cheapest paid plan
Top plan
Free trial
3 plans
Free
Free
- 3,000 emails per month
- 3,000 inbound replies per month
- 1 agent
Pro
$20/mo
- 50K emails per month
- 5 agents
- Send from your own domain
- Signed webhooks
Scale
$99/mo
- 250K emails per month
- Unlimited agents
- Per-agent allowlists and send limits
3 plans
Free
Free
- 2 mailboxes
- 1 domain
- $1 usage credit
Pro
$7/mo
- Per team, plus usage
- Unlimited mailboxes and domains
- Credit top-ups
Enterprise
Custom
- Postpaid usage
- Dedicated infrastructure
- Custom SLAs
Prices in USD, checked Oct 29, 2026 or later. Plans change often, so confirm on each tool's site before you buy.
Pros and cons
Mails.ai
- Free tier with no card
- Controls on who an agent can email
- Works with major coding agents
- Free plan allows just 1 agent
- Custom domains need Pro
- Dedicated IP is on request only
Sendmux
- Built specifically for AI agents
- No per-mailbox fees
- Works with your own email providers
- Free plan adds a Sendmux footer
- Free managed sending is very limited
- Usage costs on top of the Pro fee
Which one should you choose?
Choose Mails.ai if you want:
- Free tier with no card
- Controls on who an agent can email
- Works with major coding agents
Watch out: free plan allows just 1 agent.
Choose Sendmux if you want:
- Built specifically for AI agents
- No per-mailbox fees
- Works with your own email providers
Watch out: free plan adds a sendmux footer.
Mails.ai vs Sendmux FAQ
What is the difference between Mails.ai and Sendmux?
Mails.ai: Email API that gives AI agents their own inboxes. Sendmux: Email, calendar and file API that gives AI agents real inboxes. Both are coding tools.
Is Mails.ai or Sendmux cheaper?
Sendmux has the lower starting price: about $7 a month, against $20 for Mails.ai.
Do Mails.ai and Sendmux have free plans?
Mails.ai: Yes. Sendmux: Yes.
Who makes Mails.ai?
Mails.ai is made by Mails.ai.
Who makes Sendmux?
Sendmux is made by Sendmux.
Which should I choose, Mails.ai or Sendmux?
Choose Mails.ai if you value free tier with no card and controls on who an agent can email. Choose Sendmux if you value built specifically for ai agents and no per-mailbox fees.