https://community.bt.com/t5/General-email-queries/Error-code-501/m-p/2308048#M106260 <P><SPAN>Attempts to send emails (with @btinternet.com address ) result in&nbsp;&nbsp;</SPAN><SPAN>"Invalid mail address, must have a domain part Err.code 501". This has started to occur intermittently since about 2 weeks ago. Did a test with email sent to own address and problem still occurs.<BR /><BR />Any help or suggestions appreciated.</SPAN></P><P>&nbsp;</P><P>&nbsp;</P> Mon, 07 Aug 2023 20:09:51 GMT jedwardnolan 2023-08-07T20:09:51Z https://community.bt.com/t5/General-email-queries/Error-code-501/m-p/2308048#M106260 <P><SPAN>Attempts to send emails (with @btinternet.com address ) result in&nbsp;&nbsp;</SPAN><SPAN>"Invalid mail address, must have a domain part Err.code 501". This has started to occur intermittently since about 2 weeks ago. Did a test with email sent to own address and problem still occurs.<BR /><BR />Any help or suggestions appreciated.</SPAN></P><P>&nbsp;</P><P>&nbsp;</P> Mon, 07 Aug 2023 20:09:51 GMT https://community.bt.com/t5/General-email-queries/Error-code-501/m-p/2308048#M106260 jedwardnolan 2023-08-07T20:09:51Z https://community.bt.com/t5/General-email-queries/Error-code-501/m-p/2317670#M106910 <P>Not helpful, I'm afraid, but it's just started happening to me as well. Including to e-mail accounts I've used many times in the past and replies to e-mails I've received.</P><P>The message "Invalid mail address, must have a domain part [Err code: 501]" is definitely not telling the truth.&nbsp;</P> Sat, 30 Sep 2023 17:20:48 GMT https://community.bt.com/t5/General-email-queries/Error-code-501/m-p/2317670#M106910 Tim_G 2023-09-30T17:20:48Z