Connection error: Can't login to this server (pop3 mail import)

[Frankenstein]

Hey Guys,

i'm trying to setup my ticket forwarding, but it failed and send me some informations to root@hostname. I tryd to figure out, but dont find anything about in combination with whmcs. The problem: He cant get mails from it, but if i try to login via thunderbird or mobile client with the same credentials to the email adress over pop its working fine.

 

legend:

ip.of.whmcs.server - domain.tld - webserver for company website (nginx, mariadb, ioncube loader, php7.2 +extensions)

ip.of.mail.server - ox.domain.tld - mail server (dovecot, postfix, rspamd, imap, pop3 +extensions)

 

Here some informations from the whmcs server:
 

From root@domain.tld  Thu Dec 20 13:52:03 2018
Return-Path: <root@domain.tld>
X-Original-To: root
Delivered-To: root@domain.tld
Received: by domain.tld (Postfix, from userid 0)
    id 32AF2405B3; Thu, 20 Dec 2018 13:52:03 +0100 (CET)
From: root@domain.tld (Cron Daemon)
To: root@domain.tld
Subject: Cron <root@domain> php -q /var/www/account.domain.tld/private/whmcs/crons/pop.php
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
X-Cron-Env: <SHELL=/bin/sh>
X-Cron-Env: <HOME=/root>
X-Cron-Env: <PATH=/usr/bin:/bin>
X-Cron-Env: <LOGNAME=root>
Message-Id: <20181220125203.32AF2405B3@domain.tld>
Date: Thu, 20 Dec 2018 13:52:03 +0100 (CET)

POP Import Log
Date: 20/12/2018 13:52:01
---
Host: ox.domain.tld
Email: info@domain.tld
Connection error: Can't login to this serverHost: ox.domain.tld
Email: sales@domain.tld
Connection error: Can't login to this serverHost: ox.domain.tld
Email: support@domain.tld
Connection error: Can't login to this serverHost: ox.domain.tld
Email: network@domain.tld
Connection error: Can't login to this server

Here from the mail server:
 

Dec 20 13:49:01 ox dovecot: pop3-login: Aborted login (no auth attempts in 0 secs): user=<>, rip=ip.of.whmcs.server, lip=ip.of.mail.server, session=<UDcNjnN9vryfRb9w>
Dec 20 13:49:01 ox dovecot: pop3-login: Aborted login (no auth attempts in 0 secs): user=<>, rip=ip.of.whmcs.server, lip=ip.of.mail.server, session=<3IsNjnN9wLyfRb9w>
Dec 20 13:49:01 ox dovecot: pop3-login: Aborted login (no auth attempts in 0 secs): user=<>, rip=ip.of.whmcs.server, lip=ip.of.mail.server, session=<StsNjnN9wryfRb9w>
Dec 20 13:49:01 ox dovecot: pop3-login: Aborted login (no auth attempts in 0 secs): user=<>, rip=ip.of.whmcs.server, lip=ip.of.mail.server, session=<pSgOjnN9xLyfRb9w>
Dec 20 13:49:01 ox postfix/submission/smtpd[24089]: connect from domain.tld[ip.of.whmcs.server]
Dec 20 13:49:03 ox postfix/submission/smtpd[24089]: warning: domain.tld[ip.of.whmcs.server]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Dec 20 13:49:03 ox postfix/submission/smtpd[24089]: disconnect from domain.tld[ip.of.whmcs.server] ehlo=2 starttls=1 auth=0/1 quit=1 commands=4/5

 

 

Anybody outthere can help me fix this issue?

 

Best regards

Frankenstein

[Frankenstein]

Okay, now I know that following line:
 

SASL LOGIN authentication failed: UGFzc3dvcmQ6

means that wrong access data is used. "UGFzc3dvcmQ6" stands for hacked, which means nothing other than incorrect access data.
However, these are all correct, which I have checked several times. In addition, all accounts are accessible via Thunderbird or Mobile Client.

 

I dont get it.....