First, a big thanks and congratulations to the Outlook.com team on launching IMAP.

I'm the developer of a mail app for Android, called AquaMail, and ran into a few issues with your IMAP server.

1 - There was an issue where attachments with non-ASCII filenames (encoded using Q or B encoding in the orignal message) would be corrupted by the server when returned in a BODY / BODYSTRUCTURE response.

This has been fixed (thanks), but the size of such attachments is now reported as 0.

Compare:

BODYSTRUCTURE (("TEXT" "plain" NIL NIL NIL "7BIT" 10 1 NIL NIL NIL NIL)("image" "png" ("name" "device-2013-11-12-021749.png") NIL NIL "BASE64" 188352 NIL NIL NIL NIL) "mixed" ("boundary" "----==--bound.17948.web20m.yandex.ru") NIL NIL NIL)

This one is good, the size is 188352

BODYSTRUCTURE (("TEXT" "html" ("charset" "koi8-r") NIL NIL "QUOTED-PRINTABLE" 86 2 NIL NIL NIL NIL)("image" "png" ("name" "=?UTF-8?B?0J7RiNC40LHQutCwLVNhbXN1bmctRWNsaXBzZS5wbmc=?=") NIL NIL "BASE64" 0 NIL NIL NIL NIL) "mixed" ("boundary" "----==--bound.35339.web7h.yandex.ru") NIL NIL NIL)

This one is bad, the size is reported as 0. My code can deal with this, but it's nice to give the user an idea of an attachment's size (mobile data, etc).

2 - It would be great if the server implemented UIDPLUS for message copying (a MOVE extension would be great, too).

3 - Lacking UIDPLUS, my app tries to locate moved messages using SEARCH by Message-ID. For example:

UID SEARCH HEADER Message-ID "<*** Email address is removed for privacy ***>"

This works with every other servers where this fallback is required (not too many, actually - most support UIDPLUS these days), but Outlook.com's IMAP server always fails to locate the message.