As Microsoft continues to tweak Hotmail with measures to curtail graymail from recipients' inboxes, the ramifications for marketers become clearer.  With the latest release of Hotmail now fully released, the company points to features that may have been missed as it was first introduced.

One-click Unsubscribe

These include one-click unsubscribe, a button which users click just once to ban a particular newsletter from the inbox. "Just select (or open) a newsletter, and then choose Unsubscribe on the Sweep menu. Hotmail takes care of all the details like telling the sender to take you off their list, setting up a rule to block messages from that sender, and even cleaning up your inbox if you want," it said.

It also lets uses customize their own Instant Actions to, for example, categorize messages, sweep messages, mark messages as junk or even move messages to a folder.

The new Hotmail also comes with a number of other very user-friendly features, so no doubt adoption will increase. Marketers can try a number of tactics to manage the changes and hopefully benefit from them as well.

The case for fewer emails. Send fewer emails, at times of the day when recipients are more likely to open them. Research from MarketLive found that 39% of consumers would like to receive emails weekly from retailers with whom they have opted in.

This is more than double the second-most preferred option, twice a month, and triple that of the third-most preferred choice, 2-6 times a week. In fact, more consumers would prefer to receive emails on a monthly basis (13%) than on a daily basis (8%).

Take advantage of mobile email features. More vendors are offering them, including Microsoft's Hotmail. Mobile email open rates are steadily increasing, mostly at the expense of webmail clients, according to data from Litmus. Meanwhile, desktop open rates have stayed about the same. Opens in mobile devices experienced a 150% increase between January and July 2011, with webmail seeing a 20% decline.

Get ready for subscriber-level filtering by ISPs. Microsoft isn’t the only provider concerned about graymail and the irritation it causes subscribers. The next step some ISPs are starting to take to handle graymail, writes George Bilbrey, president of Return Path for Mediapost,  is the addition of new data points to their deliverability algorithm - metrics that allow for individual level filtering.

"This would allow email providers to deliver …graymail to the inboxes where it is wanted, and keep it from readers that would consider it spam." These metrics might include, he says:

• If the sender is in the address book.

• Replies to messages from a trusted source.

• If the message has been deleted without being opened.

• The view rate (percentage of time viewing messages from a trusted source).