Net::IMAP - Handling of NOOP untagged responses sent by Zimbra
Zimbra server sends invalid untagged responses to prevent some clients from disconnecting during long-running requests.
As they are invalid, they raise an exception in Net::IMAP, while they could be clearly identified and safely ignored.
I have opened an issue on net-imap GitHub repository along with a pull request (https://github.com/ruby/net-imap/issues/2 and https://github.com/ruby/net-imap/pull/3), but it seems I should have reported the issue here.
Can you have a look at these?