Triggered a re-import of deleted emails, what to do?

We disabled the account, that seems to have stopped import and automatic replies.

But if we enable it again, will it continue processing that queue?

How can we cancel the queue?
If we disable SMTP for that channel, will it fail that work queue or will it just keep retrying forever?

Sorry but it’s not really clear what your issue is.
No idea what queue you’re talking about (IMAP doesn’t know queues).

If you have issues outgoing via SMTP, then your mail server queue most likely is the place to look for.
You may want to provide more input - the issue template you removed usually asks for that input.