Ignore sent S/MIME Mails if S/MIME is disabled
* src/mapihelp.cpp (mapi_change_message_class): Add check for S/MIME disabled.
Outlook sets sent Mails to IPM.Note.SMIME (without suffix). When
S/MIME is disabled we need to ignore these messages. Our own
messages that are marked as S/MIME messages on send even if they
are PGP Messages have the override message class set so they are not
affected by this.
- GnuPG-Bug-Id: T2319