Exchange 2013: The specified charset is not supported.

[chris-garrett]

It looks like ms exchange does not like searching with UTF-8. I have found a few pages out there talking about it.

1. https://social.technet.microsoft.com/Forums/en-US/00bb2ec5-9951-40b4-8ec3-97e5a8f1a59f/imap-search-with-utf8?forum=exchangesvrsecuremessaging
2. MatterMail (which wraps mxk/go-imap) is trying UTF-8 first and then falling back to US-ASCII. Error on check new email: imap: unexpected completion status (EXCHANGE 2010) rodcorsi/mattermail#7

[emersion]

This happens here: https://github.com/emersion/go-imap/blob/master/client/cmd_selected.go#L95

Maybe add a Charset field in imap.SearchCriteria?

[chris-garrett]

I don't know much at all about IMAP, is there a way to determine the servers capabilities?

[emersion]

US-ASCII MUST be supported; other [CHARSET]s MAY be supported.
If the server does not support the specified [CHARSET], it MUST
return a tagged NO response (not a BAD). This response SHOULD
contain the BADCHARSET response code, which MAY list the
[CHARSET]s supported by the server.
-- (RFC 3501 page 50)

So if the server replies with BADCHARSET we should retry with ascii.

[chris-garrett]

Ok, I will take a look at this.