https://community.bt.com/t5/BT-Email-app/btconnect-e-mail/m-p/2458976#M349 <P>Hi All</P><P>My Outlook btconnect.com e-mail has suddenly stopped working and it now tells me that the e-mail address does not exist. When I try to reinstate it with a new password I get a 403 error or&nbsp;<SPAN>Fix NDR error "550 5.1.0" in Exchange Online.</SPAN></P><P><SPAN>I am not sure if this is a BT issue or a Microsoft 365 authentication problem.&nbsp;</SPAN></P><P><SPAN>Has anybody got any ideas I can try only it's caused considerble inconvenience.</SPAN></P><P><SPAN>Many thanks</SPAN></P><P><SPAN>John</SPAN></P><P>&nbsp;</P><P>&nbsp;</P> Tue, 07 Apr 2026 14:35:54 GMT DipStik 2026-04-07T14:35:54Z https://community.bt.com/t5/BT-Email-app/btconnect-e-mail/m-p/2458976#M349 <P>Hi All</P><P>My Outlook btconnect.com e-mail has suddenly stopped working and it now tells me that the e-mail address does not exist. When I try to reinstate it with a new password I get a 403 error or&nbsp;<SPAN>Fix NDR error "550 5.1.0" in Exchange Online.</SPAN></P><P><SPAN>I am not sure if this is a BT issue or a Microsoft 365 authentication problem.&nbsp;</SPAN></P><P><SPAN>Has anybody got any ideas I can try only it's caused considerble inconvenience.</SPAN></P><P><SPAN>Many thanks</SPAN></P><P><SPAN>John</SPAN></P><P>&nbsp;</P><P>&nbsp;</P> Tue, 07 Apr 2026 14:35:54 GMT https://community.bt.com/t5/BT-Email-app/btconnect-e-mail/m-p/2458976#M349 DipStik 2026-04-07T14:35:54Z https://community.bt.com/t5/BT-Email-app/btconnect-e-mail/m-p/2458978#M350 <P>This is the BT residential forum, you need to post on the business forum.</P> Tue, 07 Apr 2026 14:38:39 GMT https://community.bt.com/t5/BT-Email-app/btconnect-e-mail/m-p/2458978#M350 licquorice 2026-04-07T14:38:39Z https://community.bt.com/t5/BT-Email-app/btconnect-e-mail/m-p/2458981#M351 <P>Thanks for the information.</P><P>&nbsp;</P> Tue, 07 Apr 2026 15:04:01 GMT https://community.bt.com/t5/BT-Email-app/btconnect-e-mail/m-p/2458981#M351 DipStik 2026-04-07T15:04:01Z