Desktop Outlook failing to send e-mails, Web application working

Question

Good afternoon, we have a handful of end users that are experiencing the same issue. When attempting to send e-mails via the Outlook desktop application e-mails are sent to the outbox and never get delivered. When attempting to send the same e-mail via the online application the e-mail goes through.

Answer 1

Hi, @James Schwarz (ETS DRX US)

Welcome to the Microsoft forum.

Based on your description, I want to confirm with you whether these users have any other problems with Outlook besides not being able to send emails? Can they access their calendars?

I noticed that it worked fine when using OWA, so it seems to be a problem with the Outlook desktop client.

In addition, you can try the following troubleshooting:

• Make sure Outlook is in online mode and do not select the Work Offline button.
• Uncheck Use Cached Exchange Mode
  • In Outlook 2013/2016, click FILE > Account settings > Account settings…
  • Double click the Office 365 account, untick the Use Cached Exchange mode option.
  • Click Next > Finish.
  
• Use the SARA to check for errors and fix them:

  https://support.office.com/en-us/article/about-the-microsoft-support-and-recovery-assistant-e90bb691-c2a7-4697-a94f-88836856c72f?ui=en-US&rs=en-US&ad=US#/?env=ExRCA

• Try to create a new profile.You can refer to: Create an Outlook profile - Microsoft Support
• Update to the latest version of Outlook

I hope this helps.Please feel free to contact me for any updates.