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This guide takes a brand-new JetEmail account and a Linux server running Postfix through every step required to send authenticated mail through the JetEmail relay. By the end you’ll have Postfix forwarding all outbound mail through relay.jetsmtp.net. For deeper Postfix tuning (per-sender credentials, header rewrites, advanced TLS), see the full Postfix reference.
1

Sign up for JetEmail

Create an account at jetemail.com, then open the dashboard at dash.jetemail.com.
2

Add and verify your sending domain

  1. In the dashboard, go to Outbound → Domains
  2. Add the domain you send from (e.g. example.com)
  3. Publish every DNS record the dashboard shows (SPF, return-path, DKIM, DMARC) at your DNS provider
  4. Wait until the domain shows as verified
For a full breakdown of the records, see Email authentication.
3

Create an SMTP user

  1. Go to Outbound → SMTP in the dashboard
  2. Click Create SMTP
  3. Set a Username and strong Password
  4. Leave Quota at 0 for unlimited, or set a per-user limit
Keep the username and password ready for the next step.
4

Install SASL support

Postfix needs the SASL PLAIN modules to authenticate against the relay.
# Debian / Ubuntu
apt-get install -y libsasl2-modules

# AlmaLinux / Rocky / RHEL
dnf install -y cyrus-sasl-plain
This guide stores credentials in a texthash map, which reads /etc/postfix/sasl_passwd directly. It is built into every Postfix with no extra package and no postmap step, so it works the same on Debian / Ubuntu and on AlmaLinux / Rocky / RHEL. (The indexed types are distro-specific: hash on Debian / Ubuntu, lmdb on RHEL 9+. texthash sidesteps that split.)
5

Store the SMTP credentials

Create /etc/postfix/sasl_passwd with your SMTP user from step 3:
relay.jetsmtp.net:587    YOUR_SMTP_USERNAME:YOUR_SMTP_PASSWORD
Lock down the file permissions. With texthash there is no database to build, so there is no postmap step:
chmod 600 /etc/postfix/sasl_passwd
texthash reads /etc/postfix/sasl_passwd directly, so edits take effect on the next postfix reload. If you would rather use an indexed map, run postmap against the file and change the type in the next step to hash (Debian / Ubuntu) or lmdb (RHEL 9+).
6

Point Postfix at JetEmail

Add (or update) the following in /etc/postfix/main.cf:
relayhost = relay.jetsmtp.net:587
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = texthash:/etc/postfix/sasl_passwd
smtp_sasl_security_options = noanonymous
smtp_use_tls = yes
smtp_tls_security_level = encrypt
smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt
On AlmaLinux / Rocky / RHEL, the CA bundle lives at /etc/pki/tls/certs/ca-bundle.crt instead. Adjust smtp_tls_CAfile accordingly.
7

Reload Postfix and send a test

Validate the configuration, reload Postfix, and send a test:
postfix check
systemctl reload postfix

# Postfix provides its own sendmail, so no extra mail client is needed.
printf 'From: sender@example.com\nSubject: JetEmail relay test\n\nSent from %s\n' "$(hostname)" \
  | sendmail -f sender@example.com you@example.com
Use a From / -f address on the domain you verified in step 2, and send to a mailbox you can check (you@example.com above).
The mail command is not installed by default on most servers. sendmail ships with Postfix, so it is always available. If you prefer mail, install it first: mailutils on Debian / Ubuntu, s-nail or mailx on AlmaLinux / Rocky / RHEL.
Confirm the message arrives, then open the JetEmail dashboard’s Logs view to confirm it was accepted and authenticated. If something looks wrong, check /var/log/mail.log (or /var/log/maillog) and the SMTP block error reference.

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Common pitfalls

  • Port 25 outbound is often blocked by cloud providers and home ISPs. Stick to 587 unless you know 25 is open.
  • Wrong CA bundle path. If TLS verification fails, double-check smtp_tls_CAfile for your distro.
  • unsupported dictionary type. Indexed map types are distro-specific: hash exists on Debian / Ubuntu but not RHEL 9+, and lmdb is the reverse. This guide uses texthash, which is built into every Postfix, to avoid that. If you switch to hash or lmdb, run postconf -m first to confirm your build supports it.

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Next steps

Postfix reference

Per-sender credentials, header rewrites, advanced TLS, and troubleshooting.

Domain Lockdown

Stop other JetEmail accounts from sending as your domains.