When Sendmail encounters email addresses for domains that resolve to the local machine (even indirectly), it defaults to local delivery rather than following MX records. This behavior persists even when:
- The domain isn't in
local-host-names - MX records explicitly point elsewhere
- You only want outbound SMTP functionality
Run Sendmail's address test mode to see how it handles your domain:
sendmail -bt > 3,0 info@example.com
If you see $# local $: info in the output, Sendmail is configured for local delivery.
The most reliable approach is to rebuild Sendmail's configuration with proper mailer settings:
# Edit your sendmail.mc file dnl Disable local mail delivery for specific domains FEATURE(blacklist_recipients')dnl LOCAL_DOMAIN(example.com')REJECT LOCAL_DOMAIN(example.com')ERROR:5.7.1:Mail not accepted for local delivery # Rebuild the configuration m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf service sendmail restart
For temporary solutions or testing, modify the access database:
# Add to /etc/mail/access Connect:example.com RELAY To:example.com RELAY # Rebuild access.db makemap hash /etc/mail/access.db < /etc/mail/access service sendmail restart
After making changes, test again with:
sendmail -bt > 3,0 info@example.com
The output should now show SMTP routing instead of local delivery.
- Ensure your server isn't listed as MX for the domain
- Check DNS resolution doesn't point to localhost
- Review all class {w} and class {P} definitions
For stubborn domains that still route locally, examine full ruleset processing:
sendmail -bt -d21.12 > /tryflags es > /try smtp info@example.com
This shows the complete ruleset evaluation chain.
When configuring Sendmail as an outgoing SMTP server for web applications, you might encounter situations where emails addressed to your domain (e.g., @example.com) get delivered locally instead of following MX records. This typically happens when Sendmail considers your domain as part of its local delivery configuration.
First, verify if your domain is being treated as local by Sendmail. Run this diagnostic command:
sendmail -bt 3,0 info@example.com
If you see output ending with $# local $: info, it confirms Sendmail is handling the domain locally.
Edit your /etc/mail/sendmail.mc file and add these critical modifications:
dnl Disable local delivery for specific domains FEATURE(virtusertable', hash -o /etc/mail/virtusertable.db')dnl FEATURE(genericstable', hash -o /etc/mail/genericstable.db')dnl FEATURE(always_add_domain')dnl define(confDELIVERY_MODE', deferred')dnl
Create or modify /etc/mail/local-host-names to ensure your domain isn't listed:
# Remove or comment out your domain if present # example.com localhost localhost.localdomain
Create a mailertable entry to force external delivery:
# /etc/mail/mailertable example.com esmtp:[mail.example.com]
Then compile the changes:
makemap hash /etc/mail/mailertable < /etc/mail/mailertable make -C /etc/mail systemctl restart sendmail
Verify the changes with this command sequence:
sendmail -bv info@example.com sendmail -d60.5 -bv info@example.com
If you prefer all mail to route through your mail server:
define(SMART_HOST', [mail.example.com]')dnl define(RELAY_MAILER',esmtp')dnl define(RELAY_MAILER_ARGS', TCP $h 587')dnl
If emails still deliver locally:
- Check for cached DNS entries with
dig MX example.com - Verify Sendmail isn't falling back to local delivery with
sendmail -d8.20 -bv test@example.com - Ensure no conflicting entries in
/etc/mail/access