The Mail app is a basic email client more focused on IMAP email accounts.
The Mozilla Thunderbird is a good email client that has good support for the POP3 email accounts and receives updates often. You can see at this link how to configure an email account manually in the Mozilla Thunderbird.
https://support.mozilla.org/en-US/kb/manual-acc...
Note: This is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.