iOS visual voicemail malfunction

Jerome A 

You'll need to add "vvm.mstore.msg.t-mobile.com" to the Excluded Domains list when you create the profile at apple.nextdns.io. You do not need to add it to your profiles allowlist. 

I don't think this is a NextDNS problem for the record. I think it is a T-Mobile one. I spent many, many hours last night and my lunch today trying to figure this out because it was too interesting not to. And having just switched my work phone, I had a T-Mobile iPhone 13 to test with. 

Based on Console logs, my T-Mobile iPhone will only use a cellular interface to send Visual Voicemail (VVM) requests out on, or retrieve them over. In my VVM testing only interface "pdp_ip2" is used and it does not support public (non T-Mobile) networks. When you change your greeting or after a voicemail is left, the phone looks up the VVM address above to access the voicemail servers (like any other request). However, because VVM is the requesting app, iOS sends that NextDNS lookup over "pdp_ip2". And since the destination address is to a non-T-Mobile IP, T-Mobile silently drops the request. The phone repeatedly retires, and then gives up silently. The only way I could force a visible error was to record a new greeting and try to save it. After exactly one minute of trying, VVM returns an error ("The operation couldn't be completed. (com.apple.mobilephone error 1035.)". 

There are tests in iOS to ensure the DNS servers is working, but the test is run by a non-VVM app so it always passes. 

I suspect this is why my Verizon, AT&T, and US Mobile phones work correctly. Either they don't require a specific interface or they allow "public" requests over it. 

Taylor very interesting Taylor. Thanks ! Do you have any idea how I could find the address/domain for Fizz in Canada ?

Aurélien Faure 

I found this by installing debug profiles from Apple and watching the logs on my Mac. 

1. Download and install the "Baseband" profile from Apple. This can be done from the phone itself. You'll need to sign in with your Apple ID if prompted. https://developer.apple.com/bug-reporting/profiles-and-logs/?platform=ios&name=baseband

2. Connect your iPhone to your Mac and open "Console". It's in Utilities under Applications. 

3. Select your phone on the left and then Start at the top. You may need to answer a trust prompt on the phone the first time. 

4. Go to the Phone app, then Voicemail, then tap Greeting at the top. This will cause the phone to try to connect. 

5. In Console,  search for "hostname=" in the bar top right. 

6. This will return several entires with details of your connection and voicemail account. The full path from mine was "e5.vvm.mstore.msg.t-mobile.com" but I didnt include "e5" when I excluded the domain in the profile. 

If you don't have a Mac, you'll need to trigger a "sysdiagnose" on the phone to cause it to collect the various logs. There are two ways to trigger this, but you'll want to follow these directions since the key combo requires perfect timing. https://download.developer.apple.com/iOS/iOS_Logs/AssistiveTouch_Sysdiagnose_Logging_Instructions.pdf

Once collected, you can use AirDrop to review the logs. Or perhaps use the share action "Save to Files" and then download from iCloud using your PC. I can't really explain the process beyond here since I used my Mac. :/ 

I've also searched but I'm not able to find these domains publicly. You could always ask Fizz but you'd have to be pretty persistent, lucky, or both. 

Taylor Thank you so much to take all this time. I will try this asap. Then update everyone with the same issues. 

Taylor Ok, So. For people with Fizz operator the url used is “vl-vi-vvg001.ip.videotron.ca”. You need to exclude the following domain : “ip.videotron.ca”

Just one last question for you Taylor, do you know why it works by adding this in exclusion by creating a profile, and not just by using the app and include this only in the allowed domains list on the website ?

Aurélien Faure Woohoo! I’m glad that worked! 

Adding it to the exclude list of the profile tells the phone to use the carrier-provided DNS for that domain. This isn’t because NextDNS is blocking it. It’s because Fizz/T-Mobile only allows specific traffic over that “private interface” used for voicemail. 

We can’t change Fizz or T-Mobile’s routing choices, but we can exclude their voicemail domains so that voicemail works like intended. 

Taylor thanks for the explanation

Taylor 

THANK YOU SO MUCH

man I’ve been struggling with this for months now and I spent so many hours troubleshooting with T-Mobile. Can’t believe this worked

Taylor 

You’re a life saver, I’ve had this issue since march, countless tries and fails and finally I have my visual voicemail back!!!

Taylor wow, I created an account here just to thank you for that. I had been back and forth with T-Mobile for the past several months and went so far as to wipe and setup my phone fresh. Was about ready to dump them and apple both. Seriously would never have figured this one out and your explanation makes perfect sense. I should have known though... it's always DNS! ha!

For those of you who haven't made a mobileconfig recently, it seems the team at NextDNS really upped their game and made that tool just as wonderful as the rest of their service. Probably could use a bit more documentation for those you aren't familiar though.

bobsmith 

Wouldn’t simply adding “t-mobile.com” whitelist all of the other subdomains listed?

arteagatech I think the point of Taylor's earlier message was that it's NOT an "Allowlist" that enables this to work, and will completely bypass NextDNS for certain domains.

Instead of "Allowlist", it is the "Excluded Domains" which is only available when you sign in and use <https://apple.nextdns.io/> and click "More options" to reveal the option. Screenshot below.

Indiana Jones I think this misses the main points of my message:

1. It definitely is an issue with NextDNS and some carrier configurations, as proven by disabling NextDNS. We can’t change the carrier side configuration that causes it  

2. For those carrier configurations, no amount of NextDNS _rules changes_ (filter lists, allow lists, etc.) will fix the issue. The only currently available fix is to use the mobile configuration profile to bypass NextDNS completely for those cattier domains.