I had a fully functional Observium Enterprise installation up to last week, but no alerts are sent out any more today.

The alerts log says my alert has been sent out, but this is not the case. 

If I check the postfix queue, the email related to that alert is stuck in the queue, as it's trying to send the message to who@where, which is obviously not correct. 

The contacts are still fine though, 4 in total. Our Telegram group also did not receive any message, which has nothing to do with email. I believe something broke in the transport system.

Could anyone help to understand what is going on?

It definitely did work before. Thanks in advance for your help.

Regards,

Marco