Is the warning “You cannot send emails from Plesk because outbound connections on TCP ports 25 and 587 are blocked.” a false-positive result when the ports are accessible?

Symptoms

• The following warning appears at Tools & Settings > Mail Server Settings and Domains > example.com > Mail Settings even though the SMTP ports are not blocked:

  PLESK_WARN: You cannot send emails from Plesk because outbound connections on TCP ports 25 and 587 are blocked.

• telnet shows that the ports are open:

  # telnet smtp.gmail.com 25
  Trying 172.253.112.108…
  Connected to smtp.gmail.com.
  Escape character is ‘^]’.
  220 smtp.gmail.com ESMTP q130sm18788818ywg.52 – gsmtp

  # telnet smtp.gmail.com 587
  Trying 172.253.112.109…
  Connected to smtp.gmail.com.
  Escape character is ‘^]’.
  220 smtp.gmail.com ESMTP y206sm19186865ywa.102 – gsmtp

• iptables shows that psaadm does not have permissions for outbound SMTP connections:

  # iptables -L SMTPOUTPUT
  ACCEPT tcp — anywhere anywhere multiport dports smtp,urd,submission owner GID match mail
  ACCEPT tcp — anywhere anywhere multiport dports smtp,urd,submission owner UID match popuser
  ACCEPT tcp — anywhere anywhere multiport dports smtp,urd,submission owner UID match postfix
  ACCEPT tcp — anywhere anywhere multiport dports smtp,urd,submission owner UID match root
  LOGDROPOUT tcp — anywhere anywhere multiport dports smtp,urd,submission

Cause

Resolution

Workaround

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