Some time ago that already we speak that the Nokia N900 had not support for MMS, but now, thanks to the application based on Python called fMMS, already is possible to send MMS from our N900.
fMMS is not yet available in the repository Extras-Devel, but if you can install as .deb. Personally i don’t like install .deb files, but if you are very interested in prove fMMS is a risk that you can run or wait it in Extra-Devel 
.
After you download and install fMMS you will have to configure it, for this creates an access point of your operator to include the proxy of the operator and connect manually as MMS APN.
[youtube]http://www.youtube.com/watch?v=zdpIA24Yegw[/youtube]
Some FAQS of the author:
Solution: Make sure you type in the name EXACTLY like it says in “Internet Connections”. This means it ONLY TAKES EXISTING APNs – it does not create a new one.
Solution: Make sure you are connected to the MMS APN (you have to connect manually) – if you still get the error, try pinging the mmsc host from the terminal. If it still fails, double check your connection settings. If your provider list a “MMS Proxy” or “MMS Gateway”, input this in the HTTP Proxy settings for the connection
DON’T FORGET TO SET THE PROXY IN INTERNET CONNECTIONS
Via Maemo.org
I’ve tested plus.pl MMS configuration (Polish network) and it’s works! Thanks a lot!.. Now, I’m looking forward for multi-APN support in Maemo core..
What MMSC do i have to put for fmms for nokia N900?????
dear sir..pleas tell me how can i use my front camera.,or hw am i goin to activate so that i can use for somthing?what is the use of this front camera?please answer me as soon as posible.
Pingback: fMMS 1.0.0 for Nokia N900
Pingback: fMMS 1.0.0 for Nokia N900 | CooL HunK's Tech Googlies
plz when i send mms the reciever always complains that the text is not compactible. someone plz help me
Fmms worked for me properly until I updated the phone.
sou angolano e tenho o n900, instalei o fmms e estou com dificuldades de abrir as mms e apresenta sempre o erro de ligação, e fui para a definição de ligação do fmms
e apresenta o nome do ponto de acesso _____________ , o mmsc __________, o nome do utilizador___________, a palavra-passe____________, a proxy http__________ e o nº da porta________________. penso ser este o problema do não acesso a mms, por favor ajudem a solucionar!!!