Apple, Microsoft Working to Fix iOS 11 Mail App Issues With Outlook.com, Office 365 & Exchange Accounts
Sep 20, 2017 3:45 am PDT by Tim Hardwick
Apple says it is working closely with Microsoft to fix an issue that prevents Outlook.com, Office 365, and Exchange 2016 account holders from sending or replying to emails using Apple's native Mail app in iOS 11.

Apple published a support document on Tuesday, September 19 – the official launch date of iOS 11 – to acknowledge the issue affecting users of Microsoft email servers.


If you can‘t send an email with iOS 11 and an Outlook.com or Exchange mail account



You might see an error message that says "Cannot Send Mail. The message was rejected by the server."

If your email account is hosted by Microsoft on Outlook.com or Office 365, or an Exchange Server 2016 running on Windows Server 2016, you might see this error message when you try to send an email with iOS 11: "Cannot Send Mail. The message was rejected by the server."
On Tuesday, Microsoft also published a support note, which states that Apple's Mail app in iOS 11 "is not compatible with Outlook.com, Office 365, or Exchange Server 2016 running on Windows Server 2016".

Both companies' statements suggest they were caught off guard by the Mail app problem in iOS 11, however MacRumors is aware of several users who installed beta builds of the mobile operating system and flagged the issue with Apple as far back as July.

Despite apparently being aware of the problems for some time, both Apple and Microsoft said they are still working together to resolve the issue. Apple added that it would release a fix soon in an upcoming software update, while Microsoft offered the following workaround in the meantime.
To work around this issue, download the free Outlook for iOS client from the App Store. The Outlook for iOS client fully supports various email services, including Outlook.com, Office 365, and Exchange Server 2016. 

If you use the Mail app to sync data from Exchange Server 2016 that is running on Windows Server 2016, you can ask the system administrator to disable HTTP/2 in Windows Server 2016 as a workaround. The instructions on disabling HTTP/2 can be found in the Workaround section of KB 4032720: How to deploy custom cipher suite ordering in Windows Server 2016.
Stay tuned to MacRumors to find out as soon as Apple releases a fix for the ongoing Microsoft server issues in iOS 11.

Related Roundup: iOS 11

Top Rated Comments

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22 weeks ago
I could have sworn I saw people complaining about this during the betas. Now, 3 months later and GM released they’re talking about fixing it?
Rating: 27 Votes
22 weeks ago
I could be wrong, but for me, it seems like more of an Apple problem than a Microsoft one: If it works in iOS 10 (and it does) and doesn't on iOS 11, then the logical conclusion is Apple have changed something in the way they implement the ActiveSync protocol that breaks things
Rating: 13 Votes
22 weeks ago

MS :mad:


No, apple made the change - they should have tested the software better or even read the bug reports...!!!
Same happened in the past, it's not like it's unusual.
Rating: 9 Votes
22 weeks ago

This is up there with the removal of the AppStore in iTunes. From Mr. Cook's point of view this is a small problem. He probably said, who uses Microsoft products anymore just as he said, who uses the AppStore on the desktop. Both low percentages in his mind.


No, this is false. Compatibility with Microsoft software is important to Apple - that's why they made a big deal of demoing the iPad version of Office. The same is true in reverse for Microsoft, as they have thankfully moved on from the days when they regarded Office as just a tool to force people to use Windows everywhere. MSFT realised that people would just use Google Docs instead, if they didn't make Office great on iOS. Both companies will want this fixed asap.

As for the thing about the app store in iTunes, obviously Apple would have real data about that. It's probably true that very few people use the app store on the desktop, otherwise they wouldn't have removed it. Personally I removed it from the iTunes menu because it was illogical to download mobile phone apps on a desktop when I don't even sync my phone with the desktop. Sure, there will no doubt be a small number of people who were still doing this, just like there were a small number of people using Dashboard widgets or DVD drives. That's just the way it goes, unfortunately, same for Google when they kill services and features, same for Microsoft when they abandoned their phones.
Rating: 7 Votes
22 weeks ago

No, apple made the change - they should have tested the software better or even read the bug reports...!!!
Same happened in the past, it's not like it's unusual.


It was actually a Microsoft issue. I was the one working with Apple for my company on this for the past 2 weeks. Microsoft enabled HTTP/2 on their CAFE servers and that caused the issue. I guess its not compatible with iOS 11. It was only happening when you try to send a new email with an attachment or a reply when a signature in the thread had an icon so it attached the icon in the reply. Hope this helps.
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Yeah, no problems for me here either. Not sure why I'm not affected, as I'm also using Office 365-hosted corporate email on Mail.app and it's working fine. Actually it's working better than iOS 10, because it has fixed a bug where text would be too small to read on my phone (something to do with HTML, apparently). Now emails are displaying perfectly, and I can send/reply to emails fine too.

I do use the Outlook app for some things, but I prefer Mail.app for quickly scanning email (and because it's the default email app when clicking links). What I really like in iOS 11 is that when I drag an email from Mail.app on my iPad to another app like Notes, Evernote or Things, it creates a link back to the email. This is a killer feature for me, which will keep me on Mail.app.


Its not every O365 tenant. just the ones that Microsoft turned on HTTP/2. They are rolling the affected servers back now. plus, it was only with emails with attachments or replies with a signature with an icon.
Rating: 6 Votes
22 weeks ago

There were no changes within iOS 11 GM and the official release yesterday. The issue is still happening on tenants within O365 that have HTTP/2 turned on. I had the pleasure of working with Apple and MS over the last 2 weeks sending them logs and other information. You also have to understand, Apple does not use O365 internally or externally so they wouldn't have caught this issue. They have a lot of bug reports that people send in. Most of those users don't even try to troubleshoot by turning it off and back on again. Beta software is supposed to be run on non-production devices. So part of the troubleshooting expecting by Apple is for a restore to be done, eventually. Most people that run the public beta, its on their full time device so many of the bug reports weren't complete and others just didn't work with Apple on the issue. Plus, with everyone saying they sent a bug report, they can't get to everyone who reports a bug.



"You also have to understand, Apple does not use O365 internally or externally so they wouldn't have caught this issue."

I get that they don't use it.

That said I have been managing Exchange servers since the Exchange version 4....24 years ago. When the iPhone first came out it did not have Active Sync support, they wanted Exchange admins to turn on IMAP. It might have happened in a few places but for the most part the iPhone did not work in the corporate world.

Then Apple licensed Active Sync and that was one of the BIG reasons Enterprise adopted the iPhone after that. To not test this thoroughly test Active Sync against Microsoft's email offerings it a mistake on Apple's part. Microsoft still owns the Enterprise Email market and will for a long time. Apple has dumped on the Enterprise market enough over the last 5-10 years. Doing stuff like this only gives those MS fanboys in most Enterpise IT shops more fuel to the "Apple does not do Enterprise" fire. They are probably trying to push some Android option.

This is NOT the first iOS update to break Active Sync support.
Rating: 6 Votes
22 weeks ago

And maybe, replace iWork with Microsoft Office.


NO! Don't take away Keynote!!!!!!
Rating: 5 Votes
22 weeks ago
Our company has experienced this problem with the iOS 11 betas.

Given how many companies use Office 365, how the hell does Apple release iOS 11 with such a basic problem outstanding?
Rating: 4 Votes
22 weeks ago
The usual, Apple releasing new software with known issues. iOS 9 was the last major release I've installed on launch day :(
Rating: 4 Votes
22 weeks ago

I could have sworn I saw people complaining about this during the betas. Now, 3 months later and GM released they’re talking about fixing it?


No kidding, eh? For such high-profile companies, this really is inexcusable. Someone is not playing by the rules and following specs closely enough. But which one?

I suppose Microsoft will use this as a opportunity to promote the Outlook.app.. :p


They already are. Not surprising.
Rating: 3 Votes

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