The fact that this problem has been ongoing for TWO+ YEARS with no clearly defined fix makes me want to take my SP3 back to the store and go buy an iPad, even though I hate Apple products. I think I'm voicing the frustrations of the people here when I say that I've been searching for over an hour with no possible fix in sight, and an apparently apathetic Microsoft.

Dear Microsoft,

Your Mail App STILL has this issue: it randomly decides that it won't send any mail and so every outgoing e-mail sits in the Outbox of the app. This seems to be some kind of password-crossing issue where multiple passwords from multiple accounts get switched. However, I've been searching for over an hour and CANNOT find a fix to this problem despite the many unanswered/unresolved forums and questions regarding this 2+ yr old problem.

By the way, thank you so much for removing the ability to go into Settings > Account within the Mail App and change the password. Now I have no idea how to fix your issue even manually. Please put the setting back so I can fix it, or just release a version of the Mail App which WORKS.

Thanks a bunch,

Twixte

In the meantime, has anyone else figured out how to temporarily resolve this annoying issue? Is there a setting I can change or do I just need to completely disconnect my Microsoft account from my SP3 before I can actually send mail again?

Hello Twixte,

Do you receive any error message when the Mail App fails to send the email?

Please refer to the following article about troubleshooting the problems with Windows Store app.
http://windows.microsoft.com/en-HK/windows-8/what-troubleshoot-problems-app
1. Download and run the Apps troubleshooter.
2. Make sure the app isnt blocked by Windows Firewall
3. Try to uninstall and reinstall the Mail app.

Best regards,
Fangzhou CHEN