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Email Suddenly Now Not Sending in Outlook 2013

Level 2

I am suddenly now unable to send emails and getting the following error message;


            Server error: '550 5.7.1 <>... Relaying denied. Proper authentication required.'


Incoming Email Server set at:


Outgoing Email Server set at:


Incoming Server POP3: 110


Outgoing Server SMTP: 25


No Authentication Required Selected:


Please help as it is becoming very frustrating and have never had this problem before now.

Level 15

Hi @amhutchi . Can you try enabling Authentication.

Do you know if this problem occurred around the time your router's ip address might have changed?

The two mail servers are    .

You might like to check out use of encryption for sending and receiving mail.

Level 2

Hi David,

Thanks for your quick reply.


Have set incoming and outgoing server to:


Have now set to require Authentication.


Ports remain as where:

POP3 to 110

SMTP to 25


And Encrypted Connection to: TLS


And now seems to be working for email send.


It appeared to start after doing a computer re-start. I connect currently though a third party secure wifi service or via phone 4G by hot spotting. Will keep an eye on it and see how it now goes. Couldn't undertsand what had changed.


Regards & Thanks


Allan H

Level 15

@amhutchi . Regarding encryption, ports 25 and 587 (SMTP) and port 110 (POP3) support STARTTLS depending on version of Outlook. Port 465 (SMTP) and port 995 (POP3) use SSL/TLS.

Regarding authentication, I had to enable it after a disconnection. After another disconnection, I found that it was not needed. In some way, it depends on ip address.