If your cPanel server is a shared environment server, your server IP might be blocked by any RBL list such as SpamHaus.
As cPanel by default set the primary email as the SMTP mail IP, to enable different IPs to be send from the cPanel, you may follow the step as below,
1. Log into WHM.
2. Select Service Configuration and choose Exim Configuration Editor.
3. Find “Reference /etc/mailips for outgoing SMTP connections” and enable it.
4. Edit the file named /etc/mailips through SSH.
Replace the host name and IPs with your desired information.
By right, you are not able to change the email username from the administrator tool of the Smartermail.
However nothing is impossible from the computer as you may actually change the username through the configuration file.
To change a user’s username from SmarterMail, you may actually change the folder name of the user and configuration file of the SmarterMail to make the username change. To get this done, you MUST be the server administrator that could access to the server back-end.
1. Stop the SmarterMail services.
2. Go to the SmarterMail email folder and usually the default setting will be C:\SmarterMail\Domains\ where domain.com is your domain name.
3. Backup the file accountList.xml.
4. Edit the file accountList.xml, change the username to the new username that you want and save it.
5. Go the email user folder and usually the default folder is C:\SmarterMail\Domains\<domain.com>\<users> where the domain.com is your domain name and users is your username.
6. Change the username folder to your new username.
7. Go into the user folder, backup the file userConfig.xml.
8. Edit the file userConfig.xml and look for the userName tag. (<userName>User</userName>) Save it.
9. Start the SmarterMail services.