SMS via wifi fails

Has anyone else had any trouble sending SMS messages to non-iPhones over Wi-Fi? I’ve noticed that sometimes I can’t send SMS messages to friends with android phones when I’m connected to Wi-Fi but it works perfectly when I’m on the cellular network by itself. I am a T-Mobile subscriber.

Could you be in a location without T-Mobile WiFi calling or have WiFi calling disabled? SMS operates over a portion of the cellular connection so would likely fail if on WiFi but not in a WiFi calling area or without WiFi calling enabled.

As @JoePreiser said, SMS is being carried by the cell network itself (GSM / LTE) so I would expect this if only WiFi is available. Have not used WiFi Calling myself, but I believe that is just a VOIP service to carry voice communication. To the best of my knowledge, SMS has no fall-back to use TCP/IP in case of network unavailability.

Technically you can SMS over data connections. It just has some extra processing hoops to go through to get into the system.

Here’s a confirmation on SMS over WiFi from an Apple support page.


Does the error seen just say failed to send or something else?

How often does it happen? Where does it happen (same place)?

My gut feel is it might just be temporary network glitches with your or their network provider infrastructure. But answers to the above could potentially suggest otherwise.

Yes. I can’t send msgs to Apple users and android users in the same msg, I need to do them separately.

I don’t get an error , but the android users often don’t get the msg at all.

I also have problems sending iMessages from my iPad, to iPhones that are in my contact list. I get an error stating the msg could not be sent, but in fact the person does get my msgs.

Some Android devices have trouble with group messages of any kind.

If you message a mixed group, the messages will go over SMS.

This happens at several locations including my home. No other issues with wifi calling.

This happens at home and a few other locations that I’m on wifi with weak cell signal. Only happens sending to android phones. Otherwise full internet access. My phone try’s to send the message for 5 minuets or so then says “failed to send”.

Those Android users you’ve had the issue sending to don’t all happen to have previously used iPhones on the same numbers do they?

No. This is relatively new in the last two months

How many people/phone numbers are participating in the group text? I found AT&T limits group texts to 10 participants; not sure of T-Mos policy.

Also, are you using all phone numbers when sending messages? I use email addresses to send iMessages but with SMS you must use phone numbers.

This happens with single numbers. It dose not sound like this is a common problem. Maybe it’s time for a wipe and rebuild of my phone.

I generally send in small numbers, 3-4 at the most. I try to use phone number,s but I could have a typo and used an email address.