This answer will explain how to receive mails from your POP3 mailbox using the SeaMonkey Mail & Newsgroups tool.
To configure SeaMonkey to handle your email you will need to open the Mail & Newsgroups tool. Click on Window, then Mail & Newsgroups.
If this is the first time you have accessed the Mail & Newsgroups tool then it will automatically start the Account Wizard. As you are adding an email account, you need to click Email Account and then Next.
Enter your name. This is the name that will show up on any emails that you send. Next, enter the email address that you are sending the email from, and click Next
You will now be asked to select the type of mail server. Leave this as POP
Incoming server: pop.123-reg.co.uk
Outgoing server: smtp.123-reg.co.uk
Enter your Incoming User Name. This is the username for your POP3 mailbox.
Enter the Outgoing User Name. This is the username for your POP3 mailbox.
You now need to enter an Account Name. This is used for reference, and to help identify the email account if you have more than one.
Once you have entered this, click Next.
Finally you will be shown a summary of all the settings that you have entered. If they are all correct, click Finish button.
Now SeaMonkey will now be configured to send and receive your email.
Please note: If you are using 123-reg's SMTP server to send outgoing email, SMTP authentication must be turned on. If you are asked for a username and password, please use your mailbox username and password.