Using a cPanel server? Getting “Timeout waiting for response after 15 seconds” error or exclamation mark on some SMTP tests on MXtoolbox?
It’s quite easy to fix. First of all, you have to login to WHM and to Exim Configuration Manager. Find the “Introduce a delay into the SMTP transaction for unknown hosts and messages detected as spam” option and set it to “off”.
Now, your SMTP test should look something like this:
The problem seems to be occurring for all accounts accessed through domain name:
But not when logging into cPanel through the server’s hostname at https://server.example.com/cpanel instead.
This appears to be caused by “domain.com” using CloudFlare’s IP address for its A record and conflicting with the “Cookie IP validation”.
You should do the following:
WHM > Tweak Settings
Cookie IP validation > disabled
If you’d like to continue using “Cookie IP validation” on your server, users will need to access cPanel through the server’s IP or hostname directly to circumvent this issue.