iPhone/iPad - Cannot send mail. A copy has been placed in your Outbox. The recipient was rejected by the server

Occasionally I've seen users experience an issue where they can no longer send emails to anyone from their iPad or iPhone, they get the below error message;

"Cannot send mail. A copy has been placed in your Outbox. The recipient %name% was rejected by the server"

The issue is usually caused by the authentication (ie. username and password) failing for the email account, because it is either missing or incorrect.

I've often seen this happen after iOS updates, as passwords for email accounts aren't always preserved during the update process. As a result, the password appears to be present (when you check the settings), but actually isn't, and therefore emails won't send any longer.

To fix the issue, do the following on the problematic device(s);

• Go to Settings
• Go to Mail
  
  
• Select Accounts
  
  
• Select the account that you are having problems sending from
  
  
• Select the account again (first option at top of screen)
  
  
• Update the Domain, Username and Password fields. Even if the password appears to be in there (represented by black circles), delete whatever is in there and re-type the password
  
  
• Click Done from the top right corner. Settings should now be checked and you should get a list of ticks down the ride side of the page

If the settings saved successfully you can try sending emails again, it should now work correctly.