InReplyTo ArgumentException for a specific value

[Nevca]

Describe the bug
MimeMessage.InReplyTo calls MailboxAddress.TryParse and throws ArgumentException if it fails to parse the given value.

I can reproduce this with the following string:
[d7e8bc604f797c18ba8120250cbd8c04-JFBVALKQOJXWILKCJQZFA7CDNRQXE2LUPF6EIYLUMFGG643TPRCXQ32TNV2HA===@microsoft.com]

However, MimeMessage.References does not use MailboxAddress.TryParse, thus the same string is accepted and inserted in the references collection.

I also tested with the following code, and it is also working:
mimeMessage.Headers.Add(HeaderId.InReplyTo, "[d7e8bc604f797c18ba8120250cbd8c04-JFBVALKQOJXWILKCJQZFA7CDNRQXE2LUPF6EIYLUMFGG643TPRCXQ32TNV2HA===@microsoft.com]")

I'm somewhat confused which is the correct behavior. Shouldn't all three either throw or do not, given the same input string?

Which code should I use if I accept the example string as valid? Or should I trim the invalid characters? Is there a Util class or something I could use for trimming?

[jstedfast]

MimeKit was designed to be strict in what it will send (which requires strictness in what it would accept as values for message.InReplyTo = ..., etc) but relaxed in what it would accept (e.g. MimeMessage.Load).

Over time, I've had to dumb down the message-id parser(s) that are used for various property setters because of the need to be able to reply to messages with garbage message-ids (presumably like in your situation).

It looks like I need to do the same for the InReplyTo property setter.

[Nevca]

Thank you.

[jstedfast]

You're welcome 🙏