If you're starting Outlook Express for the first time, the new account dialog will appear automatically. If you are configuring an existing setup, go to Tools --> Accounts, delete any SeattleServer accounts that currently exist, and then click new to bring up the following window. Enter your name here as you would like it to appear to E-Mail recipients.
Select IMAP as the type of incoming mail server, and set the servers to mail.yourdomain.com and smtp.yourdomain.com. Click Next > when you're ready.
In this window, simply type your email address and click Next >.
Your Account name is your full E-Mail address, and your password should be entered here as well. Do NOT check the SPA check box.
Your IMAP account is now set up, and you should be able to receive mail. However, there are several default settings which are better adjusted, and you will at a minimum need to enable SMTP authentication to be able to send mail. To get started, click on Tools --> Accounts if you don't already have the accounts window open.
Now select the account you just added, and then click the Properties button.
For clarity, set the name of your account to be the same as your E-mail address. You may also enter an organization name here.
On the Servers tab, check the box labeled "My server requires authentication.
On the IMAP tab, change the Sent Items path to simply "Sent", instead of "Sent Items". This will keep the folder for sent mail consistent with webmail and/or other mail clients. You can delete the Sent Items folder if it has been created for you after you have changed the folder name here.
Your account is now set up and ready to go! The following is simply an overview of Outlook Express options, along with our recommendations on their settings.
First, go to the options dialog by clicking Tools --> Options.
We turn the Go directly to my Inbox option off, because it will load Local Folders/Inbox, which doesn't contain anything (messages are generally all in the Inbox on the IMAP server). You can check your messages as often as you like - shown here is the minimum setting of once per minute.
As a matter of preference, we like messages to be marked as read as soon as they are opened. So we decrease the timeout for the first option to 0 seconds.
We disable sending read receipts entirely as they compromise privacy.
We set the composition format to plain text.
We set the font to something with a fixed-width to make letters line up correctly in text mail.
You can set up a signature for yourself on this tab.
The "Purge deleted messages when leaving IMAP folders" is of special note here. When you delete messages on an IMAP server using Outlook Express, they are only marked as deleted (a line will be drawn through them). To delete them permanently, you must click Edit --> Purge Deleted Messages. This can be annoying if you have a lot of folders. This option expunges all messages marked as deleted whenever you click on a different folder if you turn it on.
With any luck, Outlook Express is now configured to access your mailbox with IMAP. All folders and mail will be stored on the server, so you will see the same mail whether you log in from another machine or webmail. Congratulations!
Old Mail Tip:
If you were using Outlook Express with POP3 previously, all of your old mail is still in Local Folders/Inbox. It is recommended that you move this into your IMAP Inbox to have all of your mail in one place, and so that it's stored in a safe place. To do this, simply go into Inbox under Local Folders, select all your mail, and drag it into the Inbox for the account you just configured. You should also move any old folders from Local Folders into your IMAP account.