I've never had an issue with this before, but now whenever I try and send a text to someone who doesn't also use an iPhone it fails to send. After a quick search, I found that this is apparently been an issue for a lot of people but none had a solution. I tried going through all the redirects from the xfinity support number, but there's no automated option for issues like this and I hit a dead end. Why is this happening only to people who switch to xfinitymobile? Why is it even happening in the first place? I don't even know where to start to try and solve it on my own, so I'm hoping someone can help me fix this.
When you have IMessage enabled you can send texts, photos, or videos to other iMessage registered users over WiFi or cellular data. These are not SMS or MMS.
When you send a text to a non iMessage registered user then you are sending an SMS or MMS over the cellular network (or WiFi Calling if enabled). SMS has a 160 character limit. MMS on Xfinity Mobile has a roughly 600kb limit and requires cellular data be enabled. You will be charged for MMS data usage.