Text to Email / SMS Gateway sent as MMS not SMS

[Ferinex]

If you send a text message to an email address, it will be sent as an MMS even if no image is attached. This means, for the recipient, that the content of the message is attached to the email as a .txt file instead of being inside the body of the email. It also means the return address will be the MMS gateway instead of the SMS gateway, so any reply sent will be an MMS unnecessarily.

[rhodey]

@Ferinex I think the issue here is that if text to email messages were sent as SMS then TextSecure would need to collect and maintain a list of all the specific SMS to email gateways on a per-provider basis. Thanks to some lame changes in the Android OS TextSecure has been forced to maintain a similar list for APN MMS configurations in ApnDefaults, this has been a major pain.

Users could probably be allowed to configure the SMS to email gateway for their provider inside of the advanced MMS settings, though people understandably have mixed feelings about adding more preferences.

[automated-signal]

GitHub Issue Cleanup:
See #7598 for more information.