I get questions similar to yours very often about our devices. Hopefully the explanation that I provide is sufficient. Below is the maximum file size for picture and video messages. Of course, this varies from device to device.
Devices that are 1X capable only can send / receive a maximum file size of 350 KB.
Devices that are Rev 0 EVDO can send / receive a maximum file size of 500 KB.
Devices that are Rev A EVDO or LTE can send / receive a maximum file size of 1200 KB.
Lowering the camera resolution will reduce the image file size.
This is largely due to the quality of camera that the device has. For example, the Droid Bionic, 8 megapixel camera, can send a larger picture message than the LG enV, 2 megapixel. The destination in which you are sending the picture(s) play a role as well. You mentioned that you are sending the pictures to your email address. May I ask who is your email provider? Below is the file size limit for emails based on the provider.
Gmail - up to 25 MB
Yahoo (free email) - up to 10 MB
Hotmail - up to 10 MB
Of course the file size is subject to change based on the email provider and whether or not you have a paid subscription for email. If the picture(s) that you are sending to your email are larger than the maximum file size for the email provider then that may be the issue. Are you having the same issue when you send a picture to another cellular device? Please respond so we can further assist.
Hope this helps...