I code a webapp for online classifieds in India. The app is also supposed to have a "message center" where you can send and receive messages. I have implemented sending and receiving messages, profiles, user model and listing messages.
Now I wonder if I "thought of everything", I have not implemented the following
Sending to a username is not implemented. The identified is the email of the user. Could this be a problem, if users change their emails I probably should use the user ID instead.
Sending to several users the same messages is not implemented. I think that it is not important for a minimum viable version.
Attaching images is not supported.
HTML messages are not supported.
Did I miss anything, did I include something unneccessary or otherwise doing it wrong? What should I implement next?