prefer X-Microsoft-Original-Message-ID, if set

outlooks SMTP-server change the Message-ID of messages
and put the original Message-ID to X-Microsoft-Original-Message-ID.

the changed Message-ID has some issues:

- outgoing messages with bcc_self enabled are shown twice
  as the self-copy got the changed Message-ID while the database uses
  the original one

- read receipts do not work as they refer to the changed message id

- in general, sender and recipient see different Message-IDs

the issues can be fixed by

(1) let all receivers use the original Message-ID

	this is what this pr is doing
    and this should fix all issues with delta-to-delta communication,
	including groups, group-images etc.
    there may be issues left in communication
	with other MUAs as they are using another Message-ID.

(2) ftr: updating the Message-ID in the database of the sender to the new one

	this requires bcc_self always enabled (which is not the case)
    and may also result easily in race conditions
    (Bob answers before Alice sees its self-sent message),
    however, has the advantage of better compatibility with other MUA.

if needed, the compatibility with other MUA could be improved by remembering
both Messages-IDs, maybe we could treat the modified as References or so,
however, i think, this could be part of another PR if we know better about
real, in the wild issues.

src/headerdef.rs

@@ -11,11 +11,20 @@ pub enum HeaderDef {
     To,
     Cc,
     Disposition,
+
+    /// Used in the "Body Part Header" of MDNs as of RFC 8098.
+    /// Indicates the Message-ID of the message for which the MDN is being issued.
     OriginalMessageId,
 
     /// Delta Chat extension for message IDs in combined MDNs
     AdditionalMessageIds,
 
+    /// Outlook-SMTP-server replace the `Message-ID:`-header
+    /// and write the original ID to `X-Microsoft-Original-Message-ID`.
+    /// To sort things correctly and to not show outgoing messages twice,
+    /// we need to check that header as well.
+    XMicrosoftOriginalMessageId,
+
     ListId,
     References,
     InReplyTo,