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Email delivery (SMTP)

To sign in, trip2g emails you a one-time code. No working email = no code = you can't get in. So a self-hosted instance needs a way to send mail. trip2g speaks plain SMTP, so any transactional-email service works — pick one below, drop its SMTP credentials into your config, done.

Two ways to skip email entirely, before you commit to a provider:

  • Sign in with Google or GitHub (OAuth). No email, no SMTP, no provider account. If OAuth login covers everyone who needs access, you don't need any of this page.
  • Don't run your own mail server. It's the worst option — details below.

See selfhosted for the full self-hosting guide; this page is only the email piece.

Why not run your own mail server?

Theoretically possible, in practice the worst option. Don't waste a day on it. Field test on a fresh Hetzner VPS:

  • Outbound port 25 is blocked by default. nc gmail-smtp-in.l.google.com 25 just times out, while nc <relay-host> 587 connects instantly. Most hosts (Hetzner, and the big clouds) block 25 outbound to fight spam.
  • A local MTA doesn't help. Install Postfix and your mail sits deferred forever — it can never reach port 25 outbound, so it is never delivered. Not to the inbox, not even to spam. It just queues.
  • Getting 25 unblocked only starts the real fight. Even with an open port you then have to win rDNS/PTR, SPF, DKIM, DMARC, and build IP reputation from zero on a cold IP. Weeks of work, and one misstep lands you on a blocklist.

Conclusion: send through a hosted relay on port 587. Don't run your own outbound MTA. The rest of this page is how to pick that relay.

Which provider?

All of these give you an SMTP username and password you paste straight into trip2g. Sorted by usefulness for a small self-host: generous forever-free tiers with plain SMTP first, trial-only and pay-as-you-go last.

The biggest free tier isn't automatically the best sender — deliverability and sender reputation vary. The Reputation column flags how each is commonly regarded for transactional mail; it's a rough signal, not a ranking, and your own domain setup (verified sender, SPF, DKIM) matters just as much.

Figures are current as of mid-2026. Free tiers change often — confirm on the provider's own pricing page before you rely on a number.

Service Free tier SMTP? API? Reputation* Catch
Brevo (ex-Sendinblue) 300/day, forever (~9,000/mo) Yes Yes Good Most generous forever-free SMTP. 300/day hard cap.
Mailjet 6,000/mo, forever Yes Yes Good 200/day cap; over-cap mail queues up to 3 days then is dropped.
Resend 3,000/mo, forever Yes Yes Strong 100/day cap. Modern, developer-focused.
Elastic Email 3,000/mo (100/day), forever Yes Yes Mixed Cheap, but shared-pool reputation is uneven; free mail carries an Elastic Email footer.
SMTP2GO 1,000/mo (200/day), forever Yes Yes Good Low monthly cap; fine for a single-owner instance.
Mailgun 100/day, forever Yes Yes Strong 1 sending domain, 1-day log retention; a card may be required at signup — verify.
Scaleway TEM 300/mo, forever Yes Yes Good Then €0.25/1,000. EU provider; needs a Scaleway account + billing set up.
Amazon SES 3,000 msg/mo — first 12 months only Yes Yes Strong Not forever-free (old 62k EC2 tier is gone). Then ~$0.10/1,000 — cheapest at volume. New accounts start in a sandbox; request production access.
Zoho ZeptoMail 10,000-email credit, ~1 month trial Yes Yes Good Trial credit, not recurring. Then ~$2.50/10,000 pay-as-you-go — very cheap.
Postmark 100/month — testing only Yes (paid) Yes Excellent Widely regarded as the deliverability benchmark for transactional mail. Real sending needs a paid plan (~$15/mo).
SendGrid (Twilio) 60-day trial, 100/day Yes Yes Strong No longer has a permanent free tier — it became a 60-day trial in 2025. Paid from ~$19.95/mo.
MailerSend 500/mo, forever Yes Yes Good Allowance was cut from 3,000 to 500/mo in Dec 2025 — check it hasn't moved again.

* As commonly recommended for transactional mail, not an invented ranking. Deliverability also depends on your own domain (verified sender, SPF, DKIM).

Plug it into trip2g

trip2g sends mail over plain SMTP. The relevant settings (env var / CLI flag):

Env var Flag Default Meaning
SMTP_HOST -smtp-host (empty = log only) Provider's SMTP server host. Empty means no mail is sent.
SMTP_PORT -smtp-port 587 SMTP port. 587 for STARTTLS is the usual choice.
SMTP_USER -smtp-user (empty) SMTP username from the provider.
SMTP_PASS -smtp-pass (empty) SMTP password / API key from the provider.
SMTP_STARTTLS -smtp-starttls true Use STARTTLS. Leave true for port 587.
MAIL_FROM -mail-from no-reply@example.com Sender address. Must be on a domain you verified with the provider, or mail is rejected.

Example /etc/trip2g.env block, using Brevo's SMTP relay:

SMTP_HOST=smtp-relay.brevo.com
SMTP_PORT=587
SMTP_USER=your-login@example.com
SMTP_PASS=<brevo SMTP key>
SMTP_STARTTLS=true
MAIL_FROM=no-reply@your-verified-domain.com

Every provider gives you the equivalent three values — host, user, pass. For Resend it's smtp.resend.com, user resend, pass = your API key. For Mailjet, in-v3.mailjet.com with an API key/secret pair. Check the provider's SMTP setup page for the exact host.

MAIL_FROM is the common gotcha: it must be an address on a domain you've added and verified (its DNS records) with the provider. An unverified sender domain gets rejected — so mail effectively only works once verification is green.

No email yet? trip2g runs fine without SMTP — it just skips sign-in emails. To bootstrap the very first login, set LOG_SIGN_IN_CODES=true, restart, trigger a sign-in, and read the code from the server log (journalctl -u trip2g). Unset it once you're in — it prints codes in plaintext.

Which should I pick?

  • Easiest free start: Brevo (300/day forever, plain SMTP), Resend, or Mailjet. All free and enough for a personal or small-team instance.
  • Best deliverability reputation: Postmark (the transactional benchmark, but paid) or Amazon SES — worth it if a code failing to arrive is a real problem for you.
  • Highest volume / cheapest: Amazon SES ($0.10/1,000) or Zoho ZeptoMail ($2.50/10,000). More setup, tiny bills.
  • Zero email at all: use Google/GitHub OAuth login and skip this page entirely.

Remember the biggest free tier isn't automatically the best sender. Start with a free option, verify sign-in email actually arrives before anything else, and only move to a paid tier when you outgrow the daily cap or need stronger deliverability.