Linux tonic.o2switch.net 4.18.0-553.30.1.lve.el8.x86_64 #1 SMP Tue Dec 3 01:21:19 UTC 2024 x86_64

//lib/firewalld/services/smtp-submission.xml

 <?xml version="1.0" encoding="utf-8"?>
<service>
  <short>Mail (SMTP-Submission)</short>
  <description>SMTP-Submission allows remote users to submit mail over port 587.</description>
  <port protocol="tcp" port="587"/>
</service>