If you want to use an email reader other than the web interface for accessing your gifmon email, I recommend thunderbird. It's easy to configure and use, and, besides, it's the one I know how to configure and use.
First, obtain thunderbird from http://www.mozilla.com/thunderbird/. Run the installer and select "standard" when prompted for install type. Go ahead and choose "launch thunderbird now" when the installer asks.
When thuderbird runs for the first time, it will bring up a dialogue for creating accounts. Select "Email account" and hit next. Fill in your name as you want it to appear in the from field of emails. For the email address, gif the full thing - i.e. "gif@gifmon.org". Hit next. You're going to want "IMAP" for the type of the incoming server. Use "gifmon.org" for both the incoming and outgoing server names. On the next page, give your username as the incoming username. For example, if your email address is "bob@gifmon.org", you'd enter just "bob" here. You can safely leave the default account name (which is just your email address) on the next page. Hit next and finish to wrap up.
Gifmon uses encryption to protect your privacy both when sending and receiving emails, so we're not quite done yet; you need to tell thunderbird about this. Right-click on your email address at the left side of the screen and select "properties". First, we're going to set up encryption for receiving messages. Choose server settings on the left side of the dialogue. Under "security settings", choose "SSL" under "use secure connections". Leave "use secure authentication" unchecked. Next we want to tell thunderbird to use encryption for sending mail. Choose "SMTP server" on the left side of the dialogue. Click on gifmon.org in the list of SMTP servers (it should be the only one) and then hit "edit". Make sure "use name and password" is checked and that your username is in the "user name" box. Remember, your username is your email address without the "@gifmon.org". For "use secure connection", pick TLS. Go ahead and click "OK" to close the account settings dialogue. Click "get mail". Thunderbird will ask you if you want to accept gifmon.org's certificate; I recommend choosing "accept this certificate permanently." Next you will be asked for your password. It's reasonably safe to allow thunderbirdIt will take longer the first time, since it needs to download the list of folders and the headers of all your messages. You can use your mouse to navigate, or you can just use "n" to go to the next unread message and the space bar to scroll through individual messages.