Every time I successfully receive a MMS on /e/OS 2.7, two days later I receive a SMS from my MNO telling that I received a SMS but that my phone was not able to receive it. Which is wrong because I always manage to read all MMS messages.
All settings (APN, MMSC, MMS proxy, MCC and MSC) have been autoconfigured automatically, and manual verification showed that they match the right MNO settings.
My MNO (RED by SFR) replied that the phone itself must report to the network the good reception of the MMS, and apparently my /e/OS does not. Have you got any idea of what setting could be responsible of this?
Since I have just changed my ISP, I can confirm that the issue was already there with the former one, enforcing the clue that this is not an ISP issue. Also, previous /e/OS versions up to 1.20 also faced the same issue.
Do you have a good mobile data connection at all times?
If I understand correctly the MMS itself is carried over Wi-Fi while the delivery receipt goes over mobile data. Especially mentioned in one source concerning the receipt is the complication derived from the APN protocol IPv4/Ipv6. Do your published APN include exactly IPv4/Ipv6 ?
Do you have a good mobile data connection at all times?
I cannot guarantee a good data connection everytime, but I received MMS messages a couple of times when I was at the heart of the city where the connection quality is usually at 100%, and still receive this SMS 2 days after.
Do your published APN include exactly IPv4/Ipv6 ?
IPv4 (only) is selected in the MMS settings.
My data is often disabled but I verified in the settings that “MMS - Send and receive MMS when data is disabled” was activated. But maybe that could be something to test in case that setting would not work: receive a MMS with data activated to check if the delivery receipt is sent?