Quick answer
ClankerMails - ClankerMails wins for most builders because its free tier is enough for real testing at very low cost, while AgentMail is better only if you need more inbox management and higher free monthly email volume.
How the free tiers compare
These two free tiers solve different problems. AgentMail’s free plan is broader on paper: 3 inboxes, 3,000 emails a month, 3 GB storage, 2 webhook endpoints, and 2 team members, plus support for custom domains and deeper agent-oriented email workflows. ClankerMails is narrower but easier to outgrow intentionally: 1 inbox, 50 messages a month, 5 MB attachments, and 1-day retention, aimed at simple bot inbox testing. If you want a free tier to prototype an email agent with multiple inboxes and some team access, AgentMail goes further. If you want a no-card sandbox to validate inbox polling, notifications, and basic inbound mail handling, ClankerMails is the cleaner fit. Paid pricing is flatter and cheaper on ClankerMails, while AgentMail gets expensive at higher tiers and leaves enterprise terms custom.
AgentMail vs ClankerMails free tier, side by side
| AgentMail FTV 47 | ClankerMails FTV 47 | |
|---|---|---|
| Free inboxes | 3 | 1 |
| Monthly email/message volume AgentMail counts emails; ClankerMails counts messages. | 3,000 emails/month | 50 messages/month |
| Storage / attachment limit Not directly comparable, but AgentMail offers much more free room. | 3 GB storage | 5 MB attachments |
| Webhook or realtime hooks ClankerMails lists notifications, but no endpoint count is provided. | 2 webhook endpoints | Real-time notifications |
| Team members | 2 team members | Not stated |
| Retention | Not stated | 1-day retention |
After you outgrow the free tier
ClankerMails uses simple flat monthly pricing, starting lower and staying cheaper through the first two paid tiers. AgentMail also uses flat pricing for its public tiers, but the jump from free to paid is larger, with Developer at $20/month and Startup at $200/month. ClankerMails starts at $9/month for Pro and $29/month for Business. For a small team, ClankerMails is the cheaper paid path. AgentMail only diverges meaningfully at Enterprise, where pricing becomes custom and usage-based.
Cost at real usage
| Usage | AgentMail | ClankerMails |
|---|---|---|
| 10 inboxes, 10,000 emails/messages per month AgentMail matches this at its Developer tier; ClankerMails matches this at Pro. | $20/mo | $9/mo |
| 50 inboxes, 100,000 emails/messages per month AgentMail's public tiers do not include a 50-inbox/100k-email midpoint, so this likely pushes to Startup or custom Enterprise; ClankerMails covers it on Business. | ~$200/mo or more | $29/mo |
| 3 inboxes, 3,000 emails/messages per month AgentMail fits within its free tier; ClankerMails exceeds its free message cap and would need Pro. | Free | ~$9/mo |
Estimates, not quotes. Usage-based rates change - verify with the vendor's pricing page before committing.
When to pick each one
Pick AgentMail when…
- You need more than one inbox on the free tier for agent workflows or multi-inbox testing.
- You expect to send or process more than 50 messages a month and want a larger free allowance.
- You need storage-heavy email use, since AgentMail includes 3 GB on free versus ClankerMails' 5 MB attachment cap and 1-day retention.
- You want to try webhooks and team collaboration on the free plan with a bit more room than a sandbox.
Pick ClankerMails when…
- You want the simplest no-credit-card sandbox to test an inbox API quickly.
- You are building bot or automation flows that only need one inbox and light inbound traffic.
- You care about retention limits and attachment caps being clearly small and predictable for testing.
- You want a cheaper first paid step, since Pro starts at $9/month versus AgentMail's $20/month Developer plan.
Bottom line
For the most common builder use case, ClankerMails is the better free-tier starting point because it gets you to a workable test setup faster and at a lower paid entry price. Pick AgentMail if your free-tier needs are broader than basic inbox testing, especially if you need multiple inboxes, higher message volume, or some team and webhook room. Pick ClankerMails if you mainly want a simple bot inbox sandbox and expect to upgrade only after validation.
Read the full listings: AgentMail and ClankerMails. Scores use the FTV methodology at /ftv. Browse more head-to-heads on /compare, or see the top-ranked free tiers on /top.