pop3 account setup failed at outlook because client was not authenticated to send anonymous mail

[Beni Santoso]

Dear All,
We have installed and deployed Microsoft Exchange Server 2019 with CU2. We can setup Outlook with MAPI services successfully. The POP3 and IMAP3 services is running well. But if we try to setup Outlook with POP3 or IMAP type always failed when it try to sending mail. It always show pop window authentication.

I configure POP3S using port 995 (SSL) and port 587 (encryption : STARTTLS)
From Exchange Management Shell, i try running command like this example :

Send-MailMessage -SmtpServer mail.mycompany-name.com -Credential $credential -From 'test@mycompany-name.com' -To 'test@mycompany-name.com' -Subject 'Test email' -Port 587 -UseSsl
Send-MailMessage : The SMTP server requires a secure connection or the client was not authenticated. The server
response was: 5.7.57 SMTP; Client was not authenticated to send anonymous mail during MAIL FROM

 

[DrB0b]

Sounds like a Receive connector issue to me. In your send mail message you are not specifying a user and pw so it is trying to use Anon creds which that receive connector will not accept due to it likely not being checked as an option on whichever Receive connector that is accepting your traffic (internal or external depending on where you are sending from).

Learning - A never ending quest for knowledge usually attained by being thrown in a situation and told to fix it NOW.