In this case you probably need to set up a password in Hamster's configuration menu and use it in Gravity's login configuration. The sorting and posting work is done by MailFilt.hst, which you can read about in Hamster's help. The last two entries are different mail lists sent to their own groups. Start the NNTP server to use Gravity or start the local POP3 server to get mail from an account. You can set Hamster to automatically start the local servers upon startup in configuration - local servers.
Scripts are useful too.
This is part of my script to get mail. I think Hamster will open several connections at once. But your ISP may have a limit. Here are some sample commands. See Hamster's help for all commands.