First check the IP(s) that may have been blocked against the firewall on your server and unblock if necessary. If your customer has been blocked, they can check their IP by going to http://www.canvashost.com/ip/ and their current IP will be displayed on the web page.
Now I will explain how to unblock an IP from the firewall:
1. Log into your WHM at https://[server_name].canvashost.com:2087 or https://[host_name].canvashost.com:2087 as root with your root password.
2. In the top left hand corner of the main page there is a field that says ‘Find’ – enter: firewall and you will see “ConfigServer Security&Firewall” at the top of the menu – click on that.
3. Scroll down until you see a field that says “Search iptables for IP address”
4. Type in the IP in question to see if it has been blocked – this will also give a reason for the block.
Try the blocked IP XX.XXX.XX.XXX: This will tell you if the IP has been blocked and the reason why – Click on the Return button
5. Scroll down to the “Remove IP address” – type in the blocked IP (XX.XXX.XX.XXX) then click the “Quick Unblock” button – Then click on the Return button
6. Scroll down to the “Ignore IP address” field, enter the IP XX.XXX.XX.XXX and click on “Quick Ignore”
Repeat steps 5 and 6 for any other blocked IPs.
This will basically remove any firewall blocks for that IP and ignore it if a bad password is used again. Make sure users are using the correct username/password.
If IMAP is working and POP is not, make sure you are using the correct settings in your POP email client. These can be discovered by logging into WHM, click on “Account Information”, then “List Accounts”, click on the cPanel icon for the account you want to manage, then click on “Email Accounts” – follow the line for the email account in question until you see the “More” icon at the end. Click on that and then select “Configure Email Client” – this will give you the settings you should be using. You also have another link next to the email account that says Change Password incase you need to do that.