K-9 Mail v6.503

What's Changed

• Tweaked theme colors (@Alecaddd, @solangevalverde, @cketti)
• Added support for HTML messages using the tag and relative links (@cketti)
• Fixed the logic to skip the trash folder when deleting messages, e.g. when deleting spam (@cketti)
• Fixed bug that could lead to messages not being marked as read on the server when they should have been (@cketti)
• Internal changes (@cketti, @schlagi123)

Full Changelog: 6.502...6.503