Hy, i have a "compute engine" hosted by google. When i try to send an email via postfix, it doesn't work.

Error log says:

postfix/smtp[16416]: 16C5820035: to=< [email protected]>, relay=none, delay=60, delays=0.15/0.02/60/0, dsn=4.4.1, status=deferred (connect to alt2.gmail-smtp-in.l.google.com[2404:6800:4003:c01::1b]:25: Network is unreachable)

When i try to ping the hostname or it's ip adress, it works fine. Is this some kind of misconfiguration?

Regards, Chris

  • 1
    Ping only tests one thing: whether or not a specific type of ICMP packet can get through. It cannot be used to test SMTP. Check all firewall rules between postfix and your mail destination.
    – EEAA
    Jan 7, 2016 at 2:22
  • Does Google allow port 25 connections within their own infrastructure to Google SMTP servers? Eliminate that as a possibility. Many ISPs/Hosts do not allow that.
    – Gmck
    Jan 7, 2016 at 3:24

1 Answer 1


Google doesn't allow outbound connections to send email. The ports 25, 465 and 587 are blocked. You will need to use a third party (like Sendgrid) to send mail. More info can be found here: https://cloud.google.com/compute/docs/tutorials/sending-mail/

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