For certain reason (multiaccount) I use an alternative IMAP client (Thunderbird) with our Domino server. Recently, I noticed that if a message comes from outside of our organization its headers are encoded as LMBCS, e.g. all Cyrillic character are prefixed with 0x05 and each characters itself is encoded in windows-1251.
This happens even though the sender used UTF-8-prefixed headers:
sent:
From: =?UTF-8?B?0JjQu9GM0Y8g0JHQsNGB0LjQvQ==?= <...>
inbox:
From: "?И?л?ь?я ?Б?а?с?и?н" <...>
There's a couple of mail robots in our organization and they somehow manage to put mail in my mailbox with UTF-8-prefixed headers.
Is there a setting to not convert the mail headers (either global or per-user)?
The problem is Thunderbird does not fully support LMBCS. When replying, it copies the headers, but replaces the characters with question marks.
Check your Person document in the Domino Directory (names.nsf on your mail server). What is the setting for 'Format preference for incoming mail'? Since you are using IMAP, you should probably have it set to "Keep in sender's format". That should eliminate LMBCS conversions entirely, so messages sent with UTF-8 headers should stay in UTF-8.
Note that in theory, it should still work even if LMBCS conversions are happening, as the UTF-8 to LMBCS conversion should work, and the LMBCS conversion to whatever your IMAP client requires (I'm guessing UTF-16?) should work. But IMAP is not exercised as heavily as other parts of Domino, so internationalization/localization issues would not entirely surprise me. What this really points out, though, is that if you can't use 'Keep in sender's format' for some reason, you're going to have to look at all the conversions that happen along the path from sender to Domino router to NSF to Domino IMAP to you, and determine where a needed conversion is going wrong -- or not happening where it should. This isn't necessarily easy to do, but if I recall correctly (it's been a while!), the NotesPeek tool can show you the header data stored in the NSF as hex.