Most likely you encountered this error in your mail client for the past months. This is because mail servers have an SMTP authentication feature enabled in them, to validate users who try to send emails through that server. This is something that is enabled by default on most of the mail servers and cPanel/WHM has this enabled by default since last year.
The ‘SMTP AUTH’ error usually happens when users try to send emails without properly authenticating their mail account in email clients such as Outlook, Thunderbird or any other mail client.
With the cPanel/WHM update, email accounts that were working fine till now may find their emails getting undelivered, showing this error message in the Exim log:
2018-04-04 04:04:04 H=(:1741 F=<firstname.lastname@example.org> rejected RCPT <email@example.com>: SMTP AUTH is required for message submission on port 587
You might ask if this is good or not – of course, is good this is why here at ChemiCloud we keep this enabled by default.
If you own a VPS Hosting plan with us and for some unknown reasons you want this disabled, since you own a dedicated environment we will do this for you – however, this is not possible on our Shared/Reseller/WordPress servers.
To combat spamming in servers and to provide secure email transmission, email clients that try to send emails without using secure transmission will be denied mail delivery through the server.
Just so you know, the option that determines this is named ‘Require clients to connect with SSL or issue the STARTTLS command before they are allowed to authenticate with the server’, which is set to ‘On’ by default, in WHM -> Exim Configuration Editor.
Indeed, it can be changed to Off but this it really depends on how you plan and configure your server and how seriously you take security.
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Email server configuration should be done in an optimal way, keeping a balance between server security and functional requirements.
While it is advisable to implement secure email practices for all users in the server, sudden updates and feature changes in cPanel/WHM may tamper with the normal user functions this is why here at ChemiCloud we offer ONLY fully managed services. Most likely you will never have to read and configure your server since our amazing team is already taking care of this 24/7. We maintain and manage email servers securely to avoid spamming and spoofing and our support team identify and fix errors in no time.