Email Addresses Lookup
This SageACT! add-on provides the ability to create a lookup of records based on a list of emails. Either type in the email addresses directly or import them from a text file (one email per line) and click the Create Lookup button.
A must-have if you're doing e-mailings: allows you to quickly identify contacts with a bad e-mail address or contacts who opted out of your mailing list.
Additional information found at BestACTAddons.com