The resulting list is guaranteed not to contain duplicated tags.
WARNING: You can no longer iterate over messages after calling this
function, because the iterator will point at the end of the list.
We do not have a function to reset the iterator yet and the only
way how you can iterate over the list again is to recreate the
message list.
Return a list of tags from all messages.
The resulting list is guaranteed not to contain duplicated tags.
WARNING: You can no longer iterate over messages after calling this function, because the iterator will point at the end of the list. We do not have a function to reset the iterator yet and the only way how you can iterate over the list again is to recreate the message list.
The function returns NULL on error.