WHM/cPanel / disable POP before SMTP
Navigate to the Tweak Settings interface, which is under Server Configuration in the WHM sidebar menu. Search for Pop-before-SMTP and activate the tweak.
For security reasons, cPanel highly recommends that you disable this functionality.
:
https://blog.cpanel.com/setting-up-a...mtp-in-cpanel/
https://serverfault.com/questions/72...op-before-smtp