DomainKeys Identified Mail (DKIM), a synthesis of email authentication work by Yahoo, Cisco, and other companies, holds a key advantage for email marketers beyond getting mail to recipients.

Yahoo and Microsoft have taken Iran off the country lists of their email services as the U.S. has imposed tougher sanctions on the Islamic country.

Yahoo has learned a lesson Microsoft picked up during the Windows Live Mail/Hotmail beta, that the less experienced users who make up the brunt of their free email services are hard to innovate for. Yahoo announced late last week it was rolling into the new Yahoo Mail some features it had dropped from the old Mail. The most obvious one: the return of checkboxes.

According to some new statistics, Gmail users are young, rich, and tech-savvy (or younger, richer, and savvier than users of Yahoo Mail and Hotmail, at least).  Gmail’s market share is also steadily – and quickly – rising.  Yet there’s some bad news for the Mountain View team, as well: their product is getting trounced overall.

Web developers will have the ability to leverage the 250 million users of Yahoo Mail as they create innovative and interesting applications based on the product; Yahoo Mail vice president John Kremer can’t wait to see what they do.

Yahoo has announced the integration of Yahoo Mail with Yahoo instant messenger. This new functionality of Yahoo messenger will apparently make it possible to send and receive instant messages right from your Yahoo Mail (beta) interface.

Just in time for Valentine’s Day, Yahoo brings two services into an integrated communications package. Yahoo Mail beta users should start to see the Messenger functionality first discussed in November 2006.

The vaunted Yahoo Mail update has been rolled out to its UK users as part of a wider beta test of the service’s new functionality.