For an SMTP monitor, we constantly get following errors:
1) "Connection timed out; connect(): -2"
2) "Nameserver error on <hostname>: Cannot connect to the name server."
We get this error with other monitors (not only SMTP), but much less frequently.
Component : CA APP SYNTHETIC MONITOR
Connection timed out is not from our public stations to ASM, It is the return from your SMTP server to the public station. So, this needs to be investigated by your network team.
For Nameserver error, please review the following: