Windows 10: Office 365 Personal - Outlook POP Account with TimeWarner/Spectrum - CANNOT SEND

I am using Outlook 365 POP with my ISP-TimeWarner Spectrum. I CANNOT send out messages and receive this error:

Sending reported error (0x800CCC0F). The connection to the server was interrupted. The Server responded: 550 5.1.0 ESMTP. server not available AUP# 0-1070. I have verified with TWC that my port settings are correct and my modem is responding. I have turned off the Defender Firewall and the McAfee Firewall. Please advise how to resolve this issue. The only way I can send mail is via the WebMail for TWC!!!

:)

 

How to enable 'send as' in Outlook (Office 365 email)


Both. In OWA (web app) the users need to select Show from:




When doing this first time, the new allowed Send As email is not shown in the From drop down list. Users need to right click their usual Send As address and select Remove, then add the new Send As address manually:




After that the new address will be shown and can be selected from the drop down list.

In Outlook desktop app users need to manually remove their usual Send As address and add the new one, thereafter the new address will be shown in From drop down list.

 

How to enable 'send as' in Outlook (Office 365 email)


Let's first check you did it correctly. No offence meant, I just mean that it's worth to check:

In O365 admin center, select Users > Active users, select your account, select Mailbox permissions > Edit:




Add the user, click Save:




I repeated my test now, the permissions were granted immediately.

Please notice that the additional users can only use your account's primary email address as Send As address. An example: if your primary email is DorseyUK@your_domain and you have additional email as info@your_domain on your account, the users can only use DorseyUK@your_domain as Send As address but not the info@your_domain address.

Maybe a pic is better to explain this:

 

How to enable 'send as' in Outlook (Office 365 email)

It makes a huge difference. You cannot set your own mailbox as a shared mailbox! It's a big NO!

In Admin panel, select Users > Active Users, select your name, select Edit in right pane. Now select Email addresses. All addresses listed here (primary and other addresses) cannot be used as shared mailbox:




If you try you will get an error message telling you it cannot be used:




You must create the shared mailboxes separately, using any of the existing personal mailboxes is out of the question.