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How to fix Microsoft Outlook / Exchange server errors, cannot send emails on iPhone 6s Plus [Troubleshooting Guide]

If you are having trouble sending or replying to emails on your iPhone 6s Plus using Outlook.com, Office 365, or Microsoft Exchange in iOS 11.0 Mail app, then you’re not alone. Several iPhone users have been complaining about a problem in which the native Mail app cannot send or reply emails from the aforementioned hosts or email accounts after upgrading to iOS 11. Apparently, it’s a software bug that needs to be addressed by Apple.

However, if you haven’t gone through an upgrade yet already encountered errors while attempting to send or reply to emails from Microsoft Outlook or Exchange servers on your iPhone 6s Plus, then it denotes that something needs to be fixed on your device, Mail app, or email account in use. This post will walk you through some step-by-step solutions that are used to deal with email errors on an iPhone. Feel free to refer to this walkthrough when needed.

But before anything else, if you have a different issue with your device, visit the troubleshooting page we’ve setup for the iPhone 6s Plus. We list down every problem we address each week in that page so try to see if we’ve already addressed your concern before. If we did, try to use the solutions we suggested and if they won’t work, then you may contact us by filling up this form.

What causes email problems to occur on your iPhone 6s Plus?


In the previous months since the iOS 11 rollout, Apple and Microsoft had collaborated in working on a fix for the stock Mail app conflict with Microsoft Exchange and Outlook.com servers. This was in response to the prevalent complaints raised by iPhone users who were prompted with an error message that says, Cannot Send Mail. The message was rejected by the server.

It turned out that the iOS 11 update had brought conflict between the stock Mail app and the Microsoft email servers. As a result, email accounts hosted by Microsoft on Outlook.com, Office 365, or Exchange Server 2016 running on Windows Server 2016 were no longer compatible with Apple’s Mail app in iOS 11.

The first workaround provided by Microsoft was to download the free Outlook for iOS client from the App Store and used that instead since it already has full support to various email services including Outlook.com, Office 365, and Exchange Server 2016. Those who used the Mail app to sync data from Exchange Server 2016 that’s running on Windows Server 2016 were advised to disable HTTP/2 in Windows Server.

Later on, Apple rolled out a minor firmware update that contains the required fix through iOS 11.0.1 and later versions. That being said, affected users are advised to install the new update so as to get the problem fixed once and for all.

For those who have updated to iOS 11.0.1 or later version but still having trouble sending or replying to Microsoft Exchange or Outlook.com emails, then that is most likely a different story. There are several factors that need to be considered in this case as the problem is seemed to be not related to iOS update conflicts. Most probably, the underlying cause lies within the Mail app settings, email account configuration, or the iPhone itself. Generally, the problem is associated with random software glitches or app malfunction on the iPhone. That being said, hardware fixing won’t be necessary.

Should you wish to troubleshoot a similar issue on your iPhone 6s Plus, the following walkthroughs will be able to assist you. Consider it a free reference then.

Solutions to email problems and errors on iPhone 6s Plus Mail app

Highlighted below are basic troubleshooting procedures and recommended workarounds that are used to deal with problems on sending and receiving emails through the iPhone’s stock Mail app. Don’t forget to create a test email after performing each method to determine whether or not the problem has been resolved. Proceed to the next applicable solution if necessary.

Verify and ensure that your iPhone is connected to the Internet.

To test your Internet connection, you can open the Safari app browser then try to open a webpage or website. If you can access the website successfully, then it means that your iPhone is connected. If not, then you need to deal with Internet connectivity issues first and once you’ve had it fixed, you will be able to send and receive emails as intended. You can use either cellular data or Wi-Fi Internet connection.

Determine whether it’s a server or Mail app issue.

Isolating the problem will help you obtain a quick solution. To find out whether or not the problem is due to your email server, try to open your email account through webmail then create a test email to send and receive through webmail. If you can successfully send and receive emails through webmail, it means that the problem is either on the Mail app or iOS device you are using. Otherwise, you’ll have to deal with email client or server issues first. If you have confirmed that the problem is not on your email server, then troubleshoot the Mail app and your iOS device.

Check your Outbox.

Emails that were not sent are routed to your Outbox. Check your Outbox, locate the email, then try to send it again. Here’s how it’s done:

  1. Open the Mail app on your iPhone.
  2. Tap Mailboxes in the upper-left corner of the Mail app screen.
  3. Tap Outbox to view emails stored in the outbox folder. If you don’t see an Outbox folder or your email was not in the Outbox folder, then it means that the email was sent.
  4. If you find the email in the Outbox folder, tap to select it.
  5. Verify and ensure that the recipient’s email address is correct and valid. Note that emails cannot be sent to invalid recipients or non-existing email addresses.
  6. Once everything is checked, tap Send.

If you still get an error while trying to send the email or the email won’t send, try the next applicable solutions.

Verify and ensure that email account credentials are correct.

If you are prompted to enter a password for your email account on the Mail app, verify and ensure that your password is correct. You can check your password by signing into your email provider’s website (webmail). If you still get a username or password error, please contact your email provider or system administrator for further assistance. They can also reset your email account information if necessary.

Verify and ensure that your email settings are correct.

iOS automatically uses the correct account settings for many email providers when you set up your email account on your iPhone. To make sure that your account settings are correct, you can compare the settings details in the Mail app to the settings for your email account. Here’s how:

  1. Tap Settings.
  2. Tap Accounts & Passwords.
  3. Then tap your email account.
  4. Tap your email address next to Account. Doing so will let you view the account information including the incoming and outgoing mail servers.

Check the recommended settings for your email account in the Mail Settings Lookup tool and make sure that they are the same as what you see on your iPhone screen. The Mail Settings Lookup tool can be found on the Apple Support website. Contact your email provider or system administrator if you don’t see the settings for your email account.

Remove your email account and set it up again.

This method has been deemed an effective solution to various types of email problems transpiring in smartphones. Should the problem be triggered by incorrect email account configuration, this can be the remedy. Before you do so, make sure that all of your email is present on your email provider’s website (webmail). You can sign in to your webmail account on your computer to check on it beforehand. Once you have verified that your emails are there, continue with these steps:

  1. Tap Settings on your iPhone 6s Plus.
  2. Tap Accounts & Passwords.
  3. Tap the email account that you want to remove.
  4. Tap Delete Account.
  5. If prompted, tap Delete email to confirm.
  6. Restart your iPhone.
  7. Then add your email account again.

You may opt for an automatic email account setup or set it up manually instead. If you opt to proceed with the latter, make sure you do have all necessary information like your email account credentials, and server settings. You may contact your email provider for this information. Otherwise, opt for automatic setup instead.

  • To do so, head over to Settings-> Accounts and Passwords-> Add Account-> Exchange. Then enter your email address and email account description, connect to the Exchange server, and sync  your contents.

Other options to consider

If none of these is able to fix the problem and that you still couldn’t send or receive Exchange or Outlook emails on your iPhone 6s Plus Mail app, then you may consider performing a factory reset as your last resort. Be sure to note though that all your personal information and critical data stored on your device’s internal memory will be erased in the process. Should you wish to proceed with a master reset or factory reset, backup your iPhone beforehand.

Or if you haven’t installed the latest iOS update on your iPhone yet, then you should try it first. After creating a backup of your iPhone data, head over to Settings-> General-> About menu, then check for any available software update for your device. If an update is available, follow the onscreen instructions to proceed with the update download and installation. You can also use iTunes to backup and update your iPhone 6s Plus. You will need to secure a computer with the latest iTunes software installed to proceed. Once you’ve got your computer ready, connect your iPhone to the computer using the supplied USB connector or Lightning cable. Open iTunes then select the options to backup and install the latest firmware update for your iPhone 6s Plus.

Again, iOS 11.0.1 and later versions contain bug fixes that will address email issues caused by iOS 11.0 firmware on the iPhone.

If the problem persists, then it’s time to seek further assistance and recommendations from your email provider or Apple Support. You can ask them to reset your email account using a dedicated tool on their end, if necessary.

Connect with us

We are always willing to help fix your problems with your Apple device. Browse through our existing troubleshooting posts or you may contact us directly by completing this form and hitting the Submit button. Make sure you provide all the necessary information about your phone and the problem so that it would be easier for us to help you.

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