Postfix SASL LOGIN authentication failed

[Teemu Rinta-aho]

I started to get a ton of these, and sshguard seems to be not catching the IPs that continuously bombard smtpd:

postfix/submission/smtpd[xxxx]: warning: unknown[xxx.xxx.xxx.xxx]: SASL LOGIN authentication failed: xyzxyzxyz
auth: pam_unix(dovecot:auth): authentication failure; logname= uid=0 euid=0 tty=dovecot

\$ cat /etc/debian_version
10.12

\$ dpkg -l | grep -e postfix -e sshguard
ii postfix 3.4.14-0+deb10u1 amd64 High-performance mail transport agent
ii postfix-sqlite 3.4.14-0+deb10u1 amd64 SQLite map support for Postfix
ii sshguard 2.3.1-1 amd64 Protects from brute force attacks against ssh

[Teemu Rinta-aho]

It was a problem with the default configuration, this was a false alarm, sorry.