What Are the Causes And How to Fix SMTP Authentication Error

Every internet user expects their emails to flawlessly work but that doesn’t work always in a perfect manner. Many websites are using PHP in order to send email through Simple Mail Transfer Protocol (SMTP). You can buy inbox SMTP server to make it easily. Occasionally, some mail severs may reject the email messages with some strange errors like SMTP Error (535): Authentication Failed. The email client uses SMTP to send the emails and to download the email clients use either IMAP or POP protocol. This authentication failed error message is usually related to the bad user email settings in the email client. The configuration of the email client always requires special attention to send or download the different email messages. 

Causes of SMTP Error 535: Authentication Failed:

From the experience in managing the email servers, the experts found that the following are the main reasons to get SMTP Error 535: Authentication failed.

  • Incorrect user name is the first cause to get authentication error in SMTP servers. The username is just same as your email id. Some SMTP servers need the various set of credentials which are separate from those used to get email message.
  • The incorrect password is another major cause of this authentication failure. The password is also same as your password in the email account. If you get an error, it is better contacting the administrator of the mail server. 
  • The wrong SMTP server name. If you give the server name incorrectly, it will also cause authentication problem.
  • Your account might be permanently or temporarily disabled. If yes, contact the administrator of the mail server.
  • Some SMTP servers require that the connection be encrypted with the special TLS or SSL. Most of the mail programs get an option which allows you to enable this specific feature.
  • Your email program might not support the authentication methods needed by the mail server. The most common authentication methods of SMTP servers include LOGIN, PLAIN, DIGEST-MD5, CRAM-MD5, and NTLM.

How to fix SMTP authentication error?

Getting errors while sending any important email message is always frustrating situation to everyone. This SMTP error 535 is one of the trickiest errors which mainly occur due to the authentication failure. With the following instructions, one can easily and quickly fix this authentication error occurred in the SMTP servers. 

  • Enabling “Allow less secure apps” feature – Due to the different security reasons, many email servers usually use the “Allow less secure apps” feature in order to protect the email accounts. You can disable this particular security feature to resolve the authentication 535 error. For that, first of all you have to login to your email account, navigate to the security settings, and then turn on “Allow less secure apps” feature.
  • Using application specific password – “Allow less secure apps” setting is not actually available for the email accounts which have already enabled the two step verification. For such accounts, you can generate application specific password to fix this authentication error. You can set this password in the setting of “send mail as” option. With the help of this application specific password in /etc/ssmtp/ssmtp.conf, you can disable two step verification using this password and resolve this SMTP server authentication error. 

Turning off this SMTP authentication in the email client system will give this authentication failure error. Luckily, you can configure SMTP authentication through this simple procedure. It probably involves modifying the configuration settings of SMTP along with some necessary changes. In your email client, you can turn on SMTP authentication. First, you have to open your email client application, go to tools -> account settings -> outing server (SMTP). In the next step, you have to select the specific outgoing server by just give a single click on it and then click the given edit button. There is security & authentication option and you should check the options of user name and password under it. Next, you have to fill in your mail account username and click ok button. In the different email servers, enabling SMTP authentication may vary according to the design of that application. 

Whenever you are experiencing this SMTP authentication error while sending any important email, first you have to find the cause of this error and correct it appropriately to send emails without any disturbance.