I've never tried this, but in the MMS screen;
Select Menu
MMS Options
Make sure that 495 KB is selected.
When I send a picture, i'll edit it before i send it to make it smaller. HTCAlbum and Media Album can do this. Otherwise you'll have to email it. If you're emailing to a verizon phone, put
1234567891@vtext.com (1234567891 is the phone number). Other carriers have their own address' also.
Hope this helps!