Emails sent from gmail bounce

Discussion in 'Server Operation' started by bluelight, Nov 20, 2017.

  1. bluelight

    bluelight New Member

    Hi everyone,

    I have a server with several clients on it, built with ISPConfig, of course and one of our mailbox users complains about the emails that are sent from comes back with this message:

    Message not delivered

    Your message couldn't be delivered to [email protected][DOT]tld because the remote server is misconfigured. See technical details below for more information.
    The response was:
    550 Please turn on SMTP Authentication in your mail client. mail-yw0-f171[DOT]google[DOT]com []:40815 is not permitted to relay through this server without authentication.

    We get and send a lot of emails from and to gmail, but none of them has this kind of problem. First I suspected that the user might have set something in his mailbox to connect to gmail and send emails through it, but I didn't find anything like this. His mailbox doesn't seem to be different from other users'.

    Has anyone met an issue like this? I haven't and I have no idea why it occurs.

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