Hey jsmyth,
thanks for the response. I am still a beginner to Linux so I have some difficulties and get confused in where to exactly find some stuff but I tried to look for the nullmailer log files in /var/spool/nullmailer. There are just 3 folders (failed, queue and tmp) which are empty and a file called “trigger” which is 0kb big.
In the syslog directory I also can’t find any indication that mails are tried to be sent by CheckMk.
However, when I connect to the server via SSH and send a test mail I also get to see something in the syslog file.
nullmailer-send[134112]: Trigger pulled.
Mar 23 10:44:37 Monitoring nullmailer-send[134112]: Queue being rescanned.
Mar 23 10:44:37 Monitoring nullmailer-send[134112]: Starting delivery, 1 message(s) in queue.
Mar 23 10:44:37 Monitoring nullmailer-send[134112]: Delivery starts: host: 172.20.0.108 protocol: smtp file: 1679564677.1257063
Mar 23 10:44:37 Monitoring nullmailer-send[134112]: From: <“.”> to: <“mailaddress”>
Mar 23 10:44:37 Monitoring nullmailer-send[134112]: Message-Id: <1679564677.467322.1257062.nullmailer@“monitoring.domain.local"l>
Mar 23 10:44:37 monitoring systemd[1]: session-121709.scope: Succeeded.
Mar 23 10:44:37 monitoring systemd[1]: session-121719.scope: Succeeded.
Mar 23 10:44:37 monitoring nullmailer-send[1257064]: smtp: Successful: 250 2.6.0 1679564677.467322.1257062.nullmailer@monitoring.domain.local [InternalId=67332202301155, Hostname=”…"] 1763 bytes in 0.109, 15.727 KB/sec Mail queued for delivery.
Mar 23 10:44:37 Monitoring nullmailer-send[134112]: File sent.
Mar 23 10:44:37 Monitoring nullmailer-send[134112]: Delivery complete, 0 message(s) remaining.
Apparently there seems to be no problem when I directly send out a test mail, but the automated mails from CheckMk do not even make it to the logs…