Apple, Microsoft Working to Fix iOS 11 Mail App Issues With Outlook.com, Office 365 & Exchange Accounts
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.
Popular Stories
Apple today updated the 14-inch MacBook Pro base model with its new M5 chip, which is also available in updated iPad Pro and Vision Pro models.
In addition, the base 14-inch MacBook Pro can now be configured with up to 4TB of storage on Apple's online store, whereas the previous model maxed out at 2TB. However, the maximum amount of unified RAM available for this model remains 32GB.
Like...
Apple today announced the next-generation iPad Pro, featuring the custom-designed M5, C1X, and N1 chips.
The M5 chip has up to a 10-core CPU, with four performance cores and six efficiency cores. It features a next-generation GPU with Neural Accelerator in each core, allowing the new iPad Pro to deliver up to 3.5x the AI performance than the previous model, and a third-generation ray-tracing ...
We didn't get a second fall event this year, but Apple did unveil updated products with a series of press releases that went out today. The M5 chip made an appearance in new MacBook Pro, Vision Pro, and iPad Pro models.
Subscribe to the MacRumors YouTube channel for more videos.
We've rounded up our coverage and highlighted the main feature changes for each device below.
MacBook Pro
M5...
Apple plans to cut production of the iPhone Air amid underwhelming sales performance, Japan's Mizuho Securities believes (via The Elec).
The Japanese investment banking and securities firm claims that the iPhone 17 Pro and iPhone 17 Pro Max are seeing higher sales than their predecessors during the same period last year, while the standard iPhone 17 is a major success, performing...
Apple on Wednesday updated the 14-inch MacBook Pro, iPad Pro, and Vision Pro with its next-generation M5 chip, but previous rumors have indicated that the company still plans to announce at least a few additional products before the end of the year.
The following Apple products have at one point been rumored to be updated in 2025, although it is unclear if the timeframe for any of them has...
Apple today updated the Vision Pro headset with its next-generation M5 chip for faster performance, and a more comfortable Dual Knit Band.
The M5 chip has a 10-core CPU, a 10-core GPU with Neural Accelerators, and a 16-core Neural Engine, and we have confirmed the Vision Pro still has 16GB of RAM.
With the M5 chip, the Vision Pro offers faster performance and longer battery life compared...
Apple on Wednesday updated the 14-inch MacBook Pro base model with an M5 chip, and there are two key storage-related upgrades beyond that chip bump.
First, Apple says the new 14-inch MacBook Pro offers up to 2× faster SSD performance than the equivalent previous-generation model, so read and write speeds should get a significant boost. Apple says it is using "the latest storage technology," ...
The new 14-inch MacBook Pro with an M5 chip does not include a charger in the box in European countries, including the U.K., Ireland, Germany, Italy, France, Spain, the Netherlands, Norway, and others, according to Apple's online store.
In the U.S. and all other countries outside of Europe, the new MacBook Pro comes with Apple's 70W USB-C Power Adapter, but European customers miss out....
Apple's AirPods Max have now been available for almost five years, so what do we know about the second-generation version?
According to Apple supply chain analyst Ming-Chi Kuo, the new AirPods Max will be lighter than the current ones, but exactly how much is as yet known. The current AirPods Max weigh 0.85 pounds (386.2 grams), excluding the charging case, making it one of the heavier...
Apple is going to launch a new version of the MacBook Pro as soon as tomorrow, so we thought we'd go over what to expect from Apple's upcoming Mac.
M5 Chip
The MacBook Pro will be one of the first new devices to use the next-generation M5 chip, which will replace the M4 chip.
The M5 is built on TSMC's more advanced 3-nanometer process, and it will bring speed and efficiency improvements. ...