Introduction
This document describes how to ensure MMS messages are successfully sent from T-Mobile iOS devices to Android recipients while using CSC.
Overview
While using the Cisco Security Connector (CSC) on T-Mobile, MMS messages sent from T-Mobile iOS devices to Android recipients can fail to successfully send. Messages to iMessage recipients are not affected.
This article refers to T-Mobile users who are using or plan to use the CSC on iPhones.
Impact
The CSC sends all DNS not on the internal domains list to the Umbrella DNS resolvers. Typically, internal domains are only required for internal company resources; however, with T-Mobile, several MMS related domains must be sent to T-Mobile in order for MMS to function correctly.
Users experiencing this issue see that group messages fail to send to Android recipients. Messages continue to send through to other iOS devices via iMessage.
Resolution
To allow MMS to be sent freely on T-Mobile while the CSC is in use, please perform these steps:
- Add eng.t-mobile.com to the internal domains list
- Sync this data to your MDM configuration. For example
- Unlink and re-link Meraki
- Re-upload a new XML or mobileconfig configuration to your MDM
- Sync this new profile to your iOS devices. Typically this step occurs automatically.
All three steps are required. Simply adding the entry to the internal domains list does not resolve this issue until it is synced to the iOS device.
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