Postfix/Dovecot authentication error

Discussion in 'Installation/Configuration' started by Jeremy007, Jan 9, 2020.

  1. Jeremy007

    Jeremy007 Member

    Dear HTF friends,

    I have been fighting with this problem for about 2 days now and i am still unable to solve it. If anyone has some advice it will be greatly appreciated.

    Setup : Multi server setup, ubuntu 16.0.4, nginx, ISPConfig 3.1.13p1

    Problem : I recently added a new site ( and mailbox ( to one of my servers but somehow i am unable to connect to the imap/smtp mailbox for that domain. Other (older) domains work properly with TLS/Starttls but i can't seem to connect to the mail server's ( inbox for this specific one unless i disable all encryption else i get "please check your email and password and try again" from windows mail mobile. I checked the mail log and the only thing i could find is the connection session starts and an immediate logout right after.
    Last edited: Jan 9, 2020
  2. Steini86

    Steini86 Active Member

    We need more info to help you with that. If the same client settings work with a different mailbox on the same server then I guess it is a DNS problem. Maybe you are connecting to a domain which is not listed in the servers SSL certificate. What are the settings of the client that work compared to the one that don't work? Only the username/password?
  3. Jeremy007

    Jeremy007 Member

    The only difference i could find is the username/password. The mail server also shows no errors.
  4. till

    till Super Moderator Staff Member ISPConfig Developer

    Which SMTP and IMAP server name did you use, if you did not use the hostname of the server, then try to use the server hostname.
  5. Jeremy007

    Jeremy007 Member

    I tired both the site's hostname and the mail server's hostname
    It's the same error i get when i try to connect my to the server.

    It gives me the following :
    Jan 13 12:27:52 mail1 postfix/smtpd[31177]: warning: unknown[]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
    Jan 13 12:27:52 mail1 postfix/smtpd[31177]: disconnect from unknown[] ehlo=1 auth=0/1 rset=1 quit=1 commands=3/4
    Jan 13 12:27:54 mail1 postfix/smtps/smtpd[31386]: SSL_accept error from[]: -1
    Jan 13 12:27:54 mail1 postfix/smtps/smtpd[31386]: warning: TLS library problem: error:140760FC:SSL routines:SSL23_GET_CLIENT_HELLO:unknown protocol:s23_srvr.c:640:
    Jan 13 12:27:54 mail1 postfix/smtps/smtpd[31386]: lost connection after CONNECT from[]
    Jan 13 12:27:54 mail1 postfix/smtps/smtpd[31386]: disconnect from[] commands=0/0
    Jan 13 12:27:56 mail1 postfix/smtpd[29605]: warning: unknown[]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
    Jan 13 12:27:57 mail1 postfix/smtpd[31174]: warning: hostname ip-38-40.ZervDNS does not resolve to address Name or service not known
  6. Steini86

    Steini86 Active Member

    The message is a bit cryptic, but means that the server and client could not agree on a secured connection. Possible problems that come to my mind right now:
    • Client does not support any of the offered cipher suites
    • Server certificate is not valid for the domain name the client connects to
    • Client does not support required TLS version (for example, client can only do TLSv1.1 and server requires TLS1.2)
    Since you do not give more information, you can use one of the usual internet pages to check your mail server encryption settings like

    Test IMAP certificate with:
    IMAP via SSL:
    openssl s_client -showcerts -connect -servername
    SMTP via TLS/StartTLS, Port 25 and 587
    openssl s_client -starttls smtp -showcerts -connect  -servername
    Last edited: Jan 14, 2020
  7. Jeremy007

    Jeremy007 Member

    Well i get connected when i try both of them. Except for port 25. So it looks as if the certs are ok, they are self signed though.
  8. Steini86

    Steini86 Active Member

    So the certs are 'not' ok (untrusted) and it depends on your client, if they are accepted or not. As you have not said anything about the client you use (or I missed it), nor present some logs from the client, it is hard to say.

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