I have a case where one user is able to receive but is unable to reply by email (using a Gmail address)
In the past they had been using a Hotmail address to successfully receive and reply to forum messages, but recently they stopped receiving anything, even though forum messages were being logged as sent by MailGun, and were not bouncing to that address according to MailGun logs.
Switching them to a Gmail account, email delivery has been getting through again, but the user’s replies to forum messages received via that Gmail address are not getting through the other way. According to the user they are not showing as bouncing, and yet according to Discourse no messages from that Gmail address are being received.
In other words the user’s Gmail address does not appear anywhere in the Skipped, Received, Bounced or Rejected email logs
Looking at Received mail log, I am seeing a bunch of undeliverable messages with no apparent sender that have been addressed to the forum’s ‘noreply’ address, as well as a few apparently deliverable spam messages without a sender to the forum’s admin address (I have thankfully never seen them appear in my inbox).
What could this lack of sender info mean? Could it be related to this user’s problem in any way?
The user forwarded me a copy of a vanished reply sent to forum topic, and the recipient address looks ok to me, though I don’t know how to test that from here (I think everything after the ‘+’ in reply address is unique to the topic and recipient)