Get a VPS
A mail server has two requirements most app hosts don’t: TCP port 25 must be open (that’s how mail arrives), and you need a domain you control. The good news: the workload is tiny — 1 vCPU / 1 GB RAM is plenty — so the cheapest tier of any of these works.
One thing that trips people up: when providers “block port 25”, they almost always mean outbound (anti-spam). Receiving mail works out of the box nearly everywhere — and receiving is the core of what your agents do (OTP codes, verification links). For sending, you either ask the provider to open it or route outbound through a relay like Amazon SES — the deliverability guide covers both.
Recommended
Section titled “Recommended”| Provider | From | Why this one | Port 25 |
|---|---|---|---|
| Vultr | $3.50/mo | Best automation: official CLI, API, and an official MCP server — your agent can drive it. Crypto top-ups (BitPay) | Inbound open; outbound via support ticket (1–2 days) |
| Contabo | $4.50/mo | Most horsepower per dollar (4 vCPU / 8 GB). Official CLI + API | Open both ways (new accounts throttled ~25 msgs/min) |
| RackNerd | ~$11/year | The rock-bottom option. Watch their flash deals | Open both ways; rDNS via ticket |
| UpCloud | $3.50/mo | Excellent automation: REST API, upctl CLI, Terraform | Inbound open; outbound via support ticket |
| Evoxt | $2.99/mo | Cheapest monthly plan; balance-based order API | Closed by default; support ticket to open |
Avoid for mail
Section titled “Avoid for mail”- DigitalOcean — officially discourages self-hosted mail and often refuses to open outbound 25.
- Hetzner (new accounts) — outbound 25 stays closed for about a month.
- Google Cloud / Azure — port 25 hard-blocked, no exceptions.
- Oracle Cloud free tier — outbound 25 effectively blocked, and idle VMs get reclaimed (a quiet mail server looks idle).
And a domain
Section titled “And a domain”Any registrar works — you’ll create MX/SPF/DKIM records by hand once, and our dns-records.sh prints exactly what to paste. If you want your agent to register domains and set DNS records via API as well, these are the automation-friendly picks:
| Registrar | .com/yr | Why this one |
|---|---|---|
| Porkbun | ~$11 | Official MCP server + full API, crypto accepted, per-key spend caps (agent-safe). First-ever domain may need one manual web purchase |
| Spaceship | ~$9 (promos from ~$3) | Clean REST API with zero gating — register, contacts, DNS all API. Bitcoin top-ups |
| Cloudflare | $10.46 (at-cost) | Official MCP + the best DNS API anywhere, one token for everything. Registrar API still beta; requires Cloudflare nameservers |
| NameSilo | ~$11 | Official MCP, crypto accepted, cheap TLD promos (.xyz from ~$1.79) |
Avoid registrars that require real-name verification with manual review — that’s a human-in-the-loop step an agent can’t pass.
No affiliate links on this page today. If we add them later they’ll be marked clearly — picks are ranked by how well they run a mail server, nothing else.