iPhone - Unable To Forward Emails via ActiveSync - "Cannot send mail; The message was rejected by the server."

Question

iPhone - Unable To Forward Emails via ActiveSync - "Cannot send mail; The message was rejected by the server."

I am troubleshooting an issue for one of our users where they are unable to forward certain emails from their iPhone. When the user goes to forward the email using the native iOS Mail App, they immediately receive an error message "Cannot send mail; The message was rejected by the server." This is Apple's description of the issue: If you can't send an email with iOS 11 and an Outlook.com or Exchange mail account - Apple Support

At this point, I have been unable to discern any common/non-standard characteristics between the emails that are unable to be forwarded. However, when we attempt to forward the SAME email in Outlook on the user's computer, we can forward it without any issues. This has become a big problem for this user because they are often in situations where they need to forward emails right away and they are not always at their computer.

Troubleshooting steps completed so far:

Attempt to forward the email using both WiFi and Cellular Data Connection. Same results.
Toggle Airplane Mode On and Off. Attempt to resend email after toggling is complete. Same results.
Restart the iPhone and re-attempt to forward the email(s) in question. Same results.
Verify that the iPhone is on the latest version of iOS (11.2.5 currently installed). Same results.
Change the ActiveSync Account Settings to be "Fetch - 15 minutes" rather than "Push". Same results.
Remove and re-add the ActiveSync Account. Same results.
Settings > General > Reset > "Reset Network Settings". Same results.
Install Outlook App and configure our Exchange Account to see if the issue persists outside of the native Mail app. Same results.
At this point, Apple had suggested that we erase all content and settings and then set the phone up as a new device. I do not believe I will be able to convince the user to do this, nor do I believe this will fix the issue (see below).

A few other pieces of information that are useful:

The emails we cannot forward from the iPhone have attachments. To my knowledge, this has not occurred with any emails that do not have attachments, but I have requested verification on this.
Attachment sizes have varied, anywhere from 4mb to 19mb (combined). Here are a few of the scenarios:
- One example had 2 attachments totaling 13mb + message size.
- One example had 3 attachments totaling 9mb + message size.
- The most recent example (from today, 1/24/2018) had 5 attachments totaling 19mb + message size.
I provided the information above to try to account for any size limitations within the iPhone Mail Client, iOS, or any Exchange Server Size Limitations when sending from Mobile Devices, but I have already been advised by Apple that no such limit exists for iOS/iOS Mail App; and separately advised by our Exchange Administrator that there is no such limit defined for our mobile devices outgoing messages.
The emails that we are unable to forward are from separate domains.
The last thing (and possibly the most important thing) that I note is that when I forward one of the emails in question to my iPhone from user's Outlook, and then attempt to forward from email to another recipient from my iPhone (using Outlook App), I receive the exact same message. I personally believe this not only validates that the issue is not device specific, nor is it specific to either configuration (iOS Mail App our Outlook Mail App). It also validates that there is not an issue with the email itself, since we are able to forward it from the Outlook Client. We also tried to forward it from OWA just for kicks - this worked fine as well.
Ironically, we are able to forward all emails in question using Good for Enterprise. Our Good for Enterprise server is separate from our Exchange Server, so I believe this also validates that it is either an Exchange or iOS/Apple issue (or the integration between the two).

I am thoroughly flummoxed by this issue, and I look forward to hearing any feedback from others if you are also seeing this in your environment.

I can provide any additional information as needed.

Thanks,

-Alec

Posted on Jan 24, 2018 12:19 PM

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Answer 1

Top-ranking reply

Carlost1234

Level 1

4 points

Feb 5, 2018 5:48 PM in response to AlecITDepartment

Al,

I have the same exact issue and have done all the same troubleshooting you have performed on 2 iPhones and have encountered the same symptoms with Native email app when (1)forwarding emails, (2)replying to emails adding an attachment, and (3)sending a new email with an attachment. iPhones are running 11.2.5, Exchange is at 2010 SP3. I have a ticket open with Microsoft and they are still dissecting some of the logs we have collected. Things I know:

1. Large iPhone user base. 99.9% of users use Verizon and have not exhibited the problem. Only 2 users use AT&T and have the issue.

2. In searching through Exchange logs I encountered one additional single entry for another device (strange) with the same issue but this happened to be an Android phone! Contacted the user, and the user explained that the Android phone works everywhere but from the user's home. When user is at home the ISP provider is, guess who? AT&T. Under AT&T, the user has the same 3 issues described above and so at home the user disconnects from Wifi to switch over to Verizon so that forwarding, replying, etc., can work.

Here is one additional test I performed which points to AT&T as the possible culprit.

1. I have two similar iPhones, 1 with a Verizon SIM (IOS 11.2.5) and the other with an AT&T SIM (IOS 11.2.2) - don't think the IOS ver. is relevant but I'm still providing that. The one with the AT&T SIM fails as described above; the Verizon SIM phone works. Now check this out - I switched the SIM's on the phones, and the issue travels with the SIM, meaning that:

a. The broken iPhone with the AT&T SIM now works fine with the Verizon SIM and am able to forward, reply, etc.

b. The iPhone that used to have the Verizon SIM and worked, not is unable to forward, reply,etc., using the AT&T SIM.

That's all I have. It will be interesting to find out what phone carrier the user experiencing the problem at your site is using. I'm still waiting for Microsoft to see if they can provide more details to establish a case for AT&T to look at, as for now they claim they have not had any reports of anyone else experiencing this issue so they are not investigating further.

Hope that helps your troubleshooting.

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