Could not issue critical alert for rule ‘Devices up/down’ to transport ‘mail’ Error: Invalid address: (From): LibreNMS@librenms
what do you have for the transport of email?
what about the email settings under global settings?
I was able to resolve the issue with this document, https://docs.microsoft.com/en-us/exchange/mail-flow-best-practices/how-to-set-up-a-multifunction-device-or-application-to-send-email-using-office-3