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An email client such as Outlook uses the Simple Mail Transfer Protocol (SMTP) to send messages. Later, to download e-mails E-mail clients use the POP or IMAP protocol. But for some reason, if authentication fails, a mail client such as Outlook generates an appropriate error message. The error “SMTP Error (535): Authentication Failed” is usually related to the incorrect user mail settings in Microsoft Outlook.

How to configure SMTP Authentication in a Mail client

Enable SMTP auth in the server

We have already seen how to enable SMTP authentication in the email client. But for this to work, the mail server must support SMTP authentication. Let’s see how our dedicated engineers facilitate this process for our customers.

SMTP Auth in Plesk server

SMTP connections on a Plesk server usually require authentication. Recently, one of our customers asked us to solve the “SMTP Error (535):

1. Authentication failed. Here, SMTP authentication was not enabled on the server. Therefore, our support engineers have solved the problem by enabling “SMTP authentication” from its Plesk server.
2. The exact sequence of steps we followed was as follows:
3. We are connected to Plesk
4. We checked the status of SMTP authorization under Tools & Settings> Mail Server Settings> Relay Options.
5. Finally, we made sure of the correct settings in Tools & Settings> Mail Server Settings> Enable SMTP Service on port 587 for all IP addresses.

Enable SMTP Authentication In cPanel

Let’s look at the steps to enable SMTP authentication in the cPanel server. SMTP authentication in cPanel allows you to send messages via POP-before-SMTP. Here, once Outlook downloads the mails, it is not necessary to authenticate again to send mails via SMTP. Typically, SMTP authentication is disabled in WHM. To enable SMTP authentication, go to WHM >> Service Configuration >> Service Manager and select the Antirelayd check box.