I think I typed mine in when I started out. If you have PHPMyAdmin, it probably wouldn't be too hard to put the information into a INSERT format - when I export my databases, the Notification table has lines that look like this:
CODE
INSERT INTO mt_notification VALUES (117, 4, NULL, 'user@yourdomain.com', NULL, '2002-05-01 14:44:10', 20020626203431, NULL, NULL);
I believe that the 117 is just whatever the next number is when being imported, which you can generate with just quotes. 4 is the blog ID that you are wanting the notifications sent via. And the date/time stamp may not be important to you, so if you leave them blank, they'll just default to 000000 strings.
CODE
INSERT INTO mt_notification VALUES ('', 4, NULL , 'user@yourdomain.com', NULL, '', '', NULL, NULL)
So if you take your email list and find/replace the stuff before the email address for all lines, and then find/replace the stuff after the email address for all lines, you would be set to enter that as a SQL query in PHPMyAdmin.
If any of this isn't clear, let me know and I'll try some more

Kristine