We have Zammad using Office 365 and OAUTH 2, with multiple groups. On occasion, there can be an issue communicating with Microsoft’s SMTP server, be it a local issue or not (or, it could be Zammad itself or the VM it runs on - but when it happens the web UI works fine).
Whenever that happens when an agent tries to send a reply, an error is logged in the ticket itself, but it doesn’t seem like Zammad queues up the email for retries?
That’s objectively quite bad, it requires the agent to realize it is a permanent failure and it also requires them to try to re-write or re-send the reply later, and remember to do that.
Every email server/handler ever made has a queue function where something gets stored once you send it, and it is then active for some days trying to resend if the first send fails.
Zammad needs something similar, in my opinion. A notification that sending failed, but that Zammad will keep trying would be a lot nicer than “connection failed, sucks to be you”.