Media EMAIL RCPT failed:553 Zabbix 6.3

[hcx23]

Hi, I have a problem configuring Media EMAIL:. Whatever port number I choose 465 for SSL or 587 for STARTLS I get:

 RCPT failed: 553

I also tried with gmx and gmail. Both failed with denied login. So I installed ssmtp and configured it.

[email protected]
mailhub=smtp.xxxx.de:465
FromLineOverride=YES
[email protected]
AuthPass=******************
hostname=erwin.***************
FromLineOverride=YES

UseTLS=YES

​

but the same error RCPT failed: 553
Has anybody an idea how to solve this.
Thanks in advance

hcx23