The first thing you need to know is that any function returning a non-const pointer to any object /must/ be unref'd when you are done with it. Since all objects in GMime now subclass GObject, you may safely use g_object_unref() (GMimeStream's may also be unref'd using g_mime_stream_unref(), but either way is fine). Don't forget that g_mime_part_get_content_object() returns a ref-counted GMimeDataWrapper object now, and so you /must/ unref it when you have finished using it. You must also remember to unref any GMimeDataWrapper object that you /set/ on a GMimePart using g_mime_part_set_content_object() as the GMimePart will now ref the content object that you set on it.

GMimeMultipart is a new class which is to be used for all multipart MIME parts rather than GMimePart (as in 1.0). There are also some subclasses of GMimeMultipart for other things.

g_mime_part_[g,s]et_boundary() have been removed (see above). You must now create a GMimeMultipart object and use g_mime_multipart_[g,s]et_boundary().

g_mime_part_add_subpart() has been replaced with g_mime_multipart_add_part().

g_mime_part_foreach() has been replaced with g_mime_multipart_foreach() and/or g_mime_message_foreach_part().

g_mime_part_get_subpart_from_content_id() has been replaced with g_mime_multipart_get_subpart_from_content_id().

Another new class is GMimeMessagePart which is to be used for all MIME parts containing an rfc822 message. All 1.0 GMimePart's representing message/rfc822 parts (as well as message/news parts?) need to be migrated over to be GMimeMessagePart objects.

GMimeMessagePartial is another class meant for handling the message/partial MIME type. All 1.0 GMimePart's holding data of this type should be replaced with GMimeMessagePartial objects.

g_mime_message_write_to_stream() and g_mime_part_write_to_stream() functions have been consolidated into a virtual method. Replace calls to these functions with g_mime_object_write_to_stream(). Note: while g_mime_part_write_to_stream() and g_mime_message_write_to_stream() still exist, it is suggested you migrate to g_mime_object_write_to_stream(). Same goes for g_mime_part_to_string() and g_mime_message_to_string().

GMimeMessage's structure has changed a bit. You will not be able to do message->header, instead you want to do ((GMimeObject *) message)->header.

g_mime_message_set_message_id() now takes a message_id argument without the encapsulating < and >'s (it now just takes the addr-spec portion of the msg-id).

GMimeFilterFrom has changed slightly, you will want to replace all calls to g_mime_filter_from_new() with g_mime_filter_from_new (GMIME_FILTER_FROM_MODE_DEFAULT) (GMIME_FILTER_FROM_MODE_DEFAULT is equivalent to (int) 0).

GMimeParser is a brand new class and gmime-parser.h has had a number of API additions. g_mime_parser_construct_part() and g_mime_parser_construct_message() still exist, however they no longer take a GMimeStream argument. Instead, they take a GMimeParser object.