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Thread: 20.04 Postfix - Dovecot user created can't send email. Why?

  1. #1
    Join Date
    Nov 2021
    Beans
    5

    Question 20.04 Postfix - Dovecot user created can't send email. Why?

    Hi:
    I just got a VPS on hostinger.
    The OS is Ubuntu 20.04.

    I am trying to make Postfix & Dovecot work.
    I have both installed and configured according to this:
    https://www.linuxbabe.com/mail-serve...l-sever-ubuntu

    I have a user mailadm on my VPS that has rwx on /home which is where mail goes.
    I logged in from Mozilla Thunderbird on my desktop (not the VPS) and it successfully created:
    /home/mailadm/Maildir with folders:.Trash cur new tmp
    It also includes some dovecot files.

    I can log in from Mozilla Thunderbird and check the mailadm mailbox.
    If I look at the VPS /var/log/syslog I see that mailadm successfully logged in with the email address: mailadm@softlinksys.com

    I delete every thing in syslog and mail.log and ftp them back to the VPS.

    I go to a different mailbox (not on the VPS) and send an email to another email address NOT on the VPS.
    I got the email with no problem (that to say, the sending email address works just fine).

    From the same mailbox I try to send an email to mailadm@softlinksys.com
    I get an error message saying 'No such user here'.
    I look at the syslog and mail.log - there is nothing about it in either log.

    The IP address is 194.163.45.150
    https://mxtoolbox.com/ clearly shows that the MX record for softlinksys.com is mail.softlinksys.com which is IP: 194.163.45.150

    Why am I unable to send an email to mailadm@softlinksys.com?
    How can I debug this problem?

  2. #2
    Join Date
    Mar 2010
    Location
    Squidbilly-Land
    Beans
    Hidden!
    Distro
    Ubuntu

    Re: 20.04 Postfix - Dovecot user created can't send email. Why?

    dovecot is for receiving only. I'm pretty certain it is an IMAP server, so the mbox files should be available from any client, assuming name resolution and open ports/firewalls from the client system to the server are working.

    postfix is for server-to-server email, typically on port 25/tcp OR authenticated client email using port 587/tcp. That means that postfix needs to understand logs for end-users and that the client system has to have port 587/tcp open to the client with working name resolution.

    MX DNS records aren't used by clients. Only server-to-server SMTP uses those records.
    If nothing is hitting the mail.log, then I'd check firewalls and name resolution. telnet {name.of.email.server} 587 will attempt a connection from the client to the server. It won't be allowed since telnet isn't doing TLS, but it will connect.
    You could also try
    openssl s_client -crlf -verify_return_error -connect mail.softlinksys.com:587
    That should connect, but not get too far. The cert should be provided back.

    VPS doesn't matter.

    Completely unrelated, but plain FTP shouldn't be used - ever. Use sftp and if your provider doesn't support that, find a better provider.

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