Just to make sure - For those who report problems with MMS:
I had problems with MMS not working properly. I then discovered that there is a setting regulating the maximum size of messages in the Settings - Apps - Messaging (or whatever it’s called in English). Although I just send pictures taken with the phone’s camera, (which, in previous versions, at least, is scaled down to a reduced resolution), increasing this setting solved my problems. So if you, like me at the outset, is not aware of this setting at all or have it set to a low value, test it out by increasing the accepted message size.
(MMS problems may be due to so many factors. The previous time I installed SF on a new phone and encountered MMS problems, it finally turned out to be caused by the phone’s SIM card being a twin card, and my carrier don’t forward MMS to those, only to main SIMs … )