Cannot Send Mail An error occurred while delivering this message

Question

Level 1

14 points

Cannot Send Mail An error occurred while delivering this message

Had anyone solved the intermittent "Cannot Send Mail An error occurred while delivering this message." pop up in the iOS Mail app? I have a user for my company who gets this at seemingly random times, many times a day. The email still sends successfully so the message is serving no purpose other than to annoy. It started on this users iPhone and has now traveled to their iPad. This user has a very large mailbox with dozens and dozens of folders but we have plenty of other people like that who don't get the message, so I don't believe this is a cause. Mail is set to sync with no limit which this person needs in order to search through their folder structure and find old mail. We are running the iOS Mail app against Office 365 but from reading other posts around the internet this seems to happen to others no matter what the mail service. That said, posts are thin on the ground, and I cannot find a lot of people with this similiar issue. Most posts with this message date back to circa 2013.

This started when the iOS 16.1 update hit. We tried just waiting it out to see if the next updates would fix it, but it hasn't. This has been going on since November 2022.

I have tried deleting the mail account from the phone and re-adding it. That did not fix it. If I install the Outlook app, it works fine, but the user wants to use the Mail app. Any help much appreciated, thank you.

iPhone XR

Posted on Mar 15, 2023 5:36 AM

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Answer 1

Sparks0829

Community Specialist

Mar 16, 2023 9:18 AM in response to fensox

Hi there fensox,

If they're seeing a popup about mail not being sent, but it's still being sent, it could potentially be a network-related issue. Does this happen when the iPhone is connected to a reliable Wi-Fi network with good signal strength? Does this message appear when connected to a different Wi-Fi network?

Also, does the message pop-up when sending emails from a different account or only the Outlook account?

Next, make sure they've updated to the most current iOS version, which is iOS 16.3.1. If needed, learn more about how to do that here: Update your iPhone or iPad - Apple Support

Thanks!

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Answer 2

Apr 14, 2023 5:42 AM in response to fensox

Did you try setting the Undo Send configuration value to "Off" yet? I just made that suggestion to the user.

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Answer 3

yfatrw00

Level 1

8 points

Apr 27, 2023 7:21 AM in response to Sparks0829

We have users experience the same thing. I contacted Apple Support and they indicate that if it's just messages on the work account, and across various devices, the issue is that the email message is momentarily unable to communicate with the O365 Exchange server, thus causing the pop-up and briefly going into the Outbox. Their recommendation was to open a case with Microsoft. Another recommendation was to utilize the Outlook app rather than the native Mail app, as delayed messages silently go into the outbox without the pop-up. All this logic makes sense, but doesn't explain why it just started happening a few months ago, and why it doesn't affect all users. Continuing to dig...

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Answer 4

yfatrw00

Level 1

8 points

Apr 27, 2023 8:06 AM in response to fensox

Did your user have the Undo Send Delay on? The users I'm seeing this most with have that feature OFF. I'm thinking if I have them enable that feature to 10 seconds, that would send the message to the outbox without creating the pop-up, and then hopefully send silently from there. Deleting the Mail app and reinstalling is also something I think I'll try, but certainly understand the hesitancy with your user!

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Answer 5

racheals14

Community Specialist

Mar 16, 2023 10:44 AM in response to fensox

Hi fensox,

Based on the details you've provided up to this point, we'd recommend contacting Apple Support from here. They'll be best equipped to investigate this a bit more, and provide any available solutions.

Take care.

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Answer 6

fensox Author

Level 1

14 points

Apr 17, 2023 4:14 AM in response to Maverick1422

That did not fix it. My users' situation is more complicated by the fact that the problem started on their iPhone and quickly traveled within a day or two to their iPad. I believe the problem resides in their Apple account somewhere and is syncing to other devices. I don't think it is an Office 365 problem (our mail backend). I am fairly confident if I killed their Apple ID and started them over with a new one that would fix it. I'm not ready to go down that road yet.

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Answer 7

fensox Author

Level 1

14 points

Apr 27, 2023 7:35 AM in response to yfatrw00

No luck here either. Unfortunately, Apple's suggestion to switch to the Outlook app doesn't fly with some of our users. They like what they know.

The not being able to connect to O365 is an odd one because the main user who started this odyssey for me has the problem on their iPhone and iPad. Which makes me think it is a setting in the Mail app that has migrated to multiple Apple devices. I'm debating deleting the mail app from both devices and adding it back. I am not sure how clean of an install that would give me or if the config would just be stored on iCloud and come right back with whatever bad setting is causing this. Plus this user has thousands of highly organized emails in folders and when I do things like that they get nervous.

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Answer 8

yfatrw00

Level 1

8 points

Apr 27, 2023 7:22 AM in response to fensox

@fensox, any updates from your troubleshooting? Apple Support tells me it's O365 being unreachable momentarily.

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Answer 9

fensox Author

Level 1

14 points

Mar 16, 2023 10:31 AM in response to Sparks0829

Thanks for the reply. The network is rock solid. It's our company WiFi and we have antennas in every room so full bars. Also, nobody else around this person is experiencing this problem and they are all on the same WiFi with the same devices. The message also appears for this person at home on their personal WiFi.

They are on 16.3.1. We have been waiting for an update hoping it would fix it to no avail.

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Answer 10

fensox Author

Level 1

14 points

Apr 14, 2023 5:31 AM in response to Maverick1422

Not yet. The person who I am helping to get this resolved hasn't been able to part with their phone long enough for the time needed to make the Apple Support call. I am hoping in the next week or so. If you figure it out, I would greatly appreciate an update on here, thank you. I've been working on this issue since November.

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Answer 11

Apr 14, 2023 2:11 PM in response to fensox

OK great - I'll update this thread as well with the results of that change or anything else I can find, although the error is very intermittent. It does appear to be an unpublished bug but it's certainly not being widely reported so not sure what specific configuration is associated with the error.

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Answer 12

fensox Author

Level 1

14 points

May 1, 2023 11:58 AM in response to nzimm

No luck here. I am hoping to uninstall the Mail app from the iPhone and iPad at the same time, then reinstall. I don't have high hopes for this working but I'm out of ideas at this point beyond nuking this guy's Apple or O365 account which he is not okay doing.

Is you issue with an Office 365 mailbox as well?

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