A few months ago I wrote about the challenges that email administrators face when asked to protect email distribution groups from spam and other unwanted emails.

I presented three options for protecting lists, each of which carried pros and cons.  Ultimately the best defense against spam to distribution lists is effective anti-spam filtering.

However anti-spam protection does not deal with mail that is not necessarily spam, but may be unwanted.  For example, a company’s “All Staff” email list may be available for use by anyone within certain guidelines, and the company wants each email checked first before they are sent to everyone to make sure inappropriate usage does not occur.

Exchange Server 2010 solves this problem for customers with a new feature called Moderated Transport.  Moderated Transport, or Email Moderation as most people will probably refer to it, is the capability to set certain recipients (either mailboxes or distribution groups) as a “moderated recipient” and designate one or more moderators who is responsible for deciding whether emails are delivered to that recipient or not.Moderated Transport operates in several ways.  Firstly, for users running Outlook 2010 or the Exchange 2010 Outlook Web App (the new name for Outlook Web Access) they will receive an on screen notification that the recipient they are sending to is a moderated recipient.

After the message is sent instead of delivering to the recipient it is instead sent to an arbitration mailbox.  The designated moderators are then each sent a message notifying them of a new email requiring moderation.  If the moderators are running Outlook 2010 or Outlook Web App they will see a clear explanation of what is required of them.  For users running older versions of Outlook they will see the traditional voting buttons instead, which will allow them to perform their moderation duties.

As mentioned earlier there can be multiple moderators assigned to a moderated recipient.  In fact this is wise so that any staff absences or other distractions don’t hold up delivery of messages.  Even though there are multiple moderators only one is required to make a moderation decision.  Once a moderator has approved or rejected a message all other moderators have the moderation request automatically removed from their Inbox to save on clutter and confusion.

There are a few other caveats for email moderation that customers should be aware of.  It is only applied by Exchange Server 2010 Hub Transport servers.  If an organization still has Exchange Server 2007 Hub Transport servers anywhere in the network they will ignore moderation settings and deliver all emails to their recipients.

Any groups that are nested within other groups also need to be considered.  Moderation needs to occur for all moderated groups, even those nested within another moderated group that has already had the message approved.  This is, however, unless an override flag has been configured to allow a parent group’s moderation to apply to all groups nested within it, which is useful to prevent child group moderators from rejecting messages that other parent moderators have already approved.

Finally, email moderation is not intended to completely replace other delivery restriction settings.  Those restrictions can still be applied and will take precedence over moderation settings.

Moderated Transport is a very useful new feature of Exchange Server 2010 that many organizations will be able to benefit from immediately.