Is there a way to import or export the blocked-sender list from one e-mail account to another?

The answer of course is, Yes.

If you're using Microsoft Outlook 2003, the procedure is fairly easy.

Click on Tools, select Options.
Click on the Preferences tab, click the Junk E-mail button .
Click the Blocked Senders tab in the resulting dialog.
Click the Export to File button.
Save the file to your desktop.
Transfer that file to the computer with the other account.

Repeat, but this time import the file.

It's much harder to do this in Outlook Express, but it is possible.

(Note: before doing any work in your registry it is important to create a backup first, to do this click on File, Export, name the file according to the date, and save it to your desktop, this may take several minutes, wait until the process is finished.)

Click on Start, Run, and type Regedit

Navigate to the key HKEY_CURRENT_USER\Identities

Below this key, you'll find one or more identity code subkeys consisting of letters and numbers in curly brackets {}.

If there's more than one, click each in turn and examine the Username value in the right-hand pane to find out which corresponds to the Outlook Express identity you normally use.

Leave that one highlighted and open its subkey Software\Microsoft\Outlook Express\5.0\Block Senders, (the number 5.0 is valid even if you're using OE6.)

Right-click this key and choose Export, exporting just the selected branch to an REG file.
Saving the file to your desktop.

Transfer the REG file to the computer containing the other e-mail account by doing the following.

Click on Start, Run, type in Regedit
Export a backup of your registry to your desktop.

Navigate to HKEY_CURRENT_USER\Identities

Identify the subkey which is the one corresponding to the main Outlook Express identity.

Launch WordPad and use it to open the REG file.

Use Find/Replace to replace the old identity code with the code for the new account.

Save the REG file and double-click to launch it, confirming that you want to merge its contents into the Registry.

Launch OE and click on Tools, Message Rules, Blocked Senders List to confirm that the transfer worked.