SMTP Authentication is the process by which an ISP’s clients authenticate themselves with the mail server to which they intend to send an email. No one can send email via any mail server; mail servers will only allow legitimate users to send an email.<\/p>\n\n\n\n
How it operates:<\/strong><\/p>\n\n\n\n When a user sends an email, the user’s mail client (Outlook, Outlook Express, Thunderbird, etc.) authenticates itself to the mail server by providing the email account’s username and associated password. If these credentials are valid, the user’s mail is accepted and processed before being relayed to the intended recipient. If authentication fails, the user’s mail client generates an appropriate error message.<\/p>\n\n\n\n 1. Incorrect Username and Password<\/strong><\/p>\n\n\n\n When the username and password for the Email client are entered incorrectly, Error 535 occurs. Using the incorrect mail server can also result in authentication failures.<\/p>\n\n\n\n Typically, such inconsistencies in email login and password are logged in the mail server’s logs. This greatly aids in locating the specific email account that is causing problems.<\/p>\n\n\n\n 2. Account Disabled<\/strong><\/p>\n\n\n\n Similarly, accounts may be disabled for a variety of reasons, including past-due payments or spamming. Additionally, this will result in SMTP Error (535): Authentication was unsuccessful.<\/p>\n\n\n\n Thus, it is worthwhile to log into the control panel and check the status of both the customer and email accounts.<\/p>\n\n\n\n 3. SMTP Authentication<\/strong><\/p>\n\n\n\n Additionally, if your email client does not have SMTP authentication enabled, this can result in an error. We’ll now examine how to enable SMTP authentication on both the server and client sides.<\/p>\n\n\n\n When the email client’s SMTP authentication is disabled, errors such as “Server says: SMTP Error (535): Authentication failed: Authentication failure” appear.<\/p>\n\n\n\n Fortunately, configuring SMTP authentication is a straightforward process. This procedure entails modifying the SMTP configuration settings and making necessary modifications.<\/p>\n\n\n\n To enable SMTP authentication in Mozilla Thunderbird.<\/strong><\/p>\n\n\n\n Enable SMTP Auth in Plesk server<\/strong><\/p>\n\n\n\n Enable SMTP Authentication In cPanel<\/strong><\/p>\n\n\n\n Let’s take a look at the steps required to enable SMTP authentication on a cPanel server. In cPanel<\/a>, SMTP authentication enables the sending of messages via POP-before-SMTP. Once Outlook has downloaded the emails, there is no need to re-authenticate in order to send emails via SMTP.<\/p>\n\n\n\n SMTP authentication is typically disabled by default in WHM. To enable SMTP Authentication, navigate to WHM >> Service Configuration >> Service Manager and check the Antirelayd option.<\/p>\n\n\n\nWhat Causes \u201cError 535: Authentication failed\u201d<\/strong>?<\/h2>\n\n\n\n
How to configure SMTP Error 535 Authentication Failed in a Mail client<\/strong><\/strong><\/h2>\n\n\n\n
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