My testing has found the following domains work to send an MMS with picture attachments to my Public Mobile phone (and probably Koodo & Telus Mobility as well). Original email "from" address is preserved, allowing direct reply to an email over MMS as well. Your phones mobile data must be ON to receive.
##########@mms.mb.telus.com
##########@msg.koodomobile.com
##########@mms.telusmobility.com
For plain SMS, where attachments will be stripped, and SMS will be from "999-999-9999". These will still come through with mobile data OFF.
##########@msg.telusmobility.com
##########@msg.telus.com
Sending an SMS to 999-999-9999 results in a reply from 4686 "999-999-9999 doesn't accept replies. Reply to the email address."
My testing shows the attachment size limit is around 500KB. JPG Images larger than that will still go through but the gateway will automatically scale/reduce the image. Other arbitrary attachment types can also be sent, up to 500KB, including WAV/MP3 which is useful for from 3rd party voicemail notifications that include the recording as an attachment.
