Maybe, when reading Postini documentation you've come across something called "wide_account" flag. However, it's hidden so deep in the documentation hierarchy that most of the people never see it, unless they are specifically digging for it.

Or, maybe, you're syncing your LDAP with Postini and receiving "Differing mail hosts" and you're trying to solve the problem. The other error you're receiving might be "Error 451 Recipients not all at same mail host - psmtp". This way or the other, it might be a good time to learn what is "Wide_Account" flag, when (and how) it should be used?

Well, in some scenarios, you Postini account can (or should) look like this:
  • Email Config 1 (London)
    • London Users Org
  • Email Config 2 (New York)
    • New York Users Org
  • Email Config 3 (Singapore)
    • Singapore Users Org
What is special in this configuration is that users from the same email domain are distributed over multiple email configs. When this kind of configuration can be applicable? Well, in many scenarios, really. 

Imagine, that you are running Microsoft Exchange environment for multi-national company. You have several Microsoft Exchange servers running, let's say, in London, New-York and  Singapore. However, all email addresses are unified to the same email domain ( in our example).

So, you've setup the above structure in your Postini account. Now, you need to add users, right? You can do it either via Google Apps Sync for Email Security (look for my post on tips-and-tricks for GADS) or via simple Postini batch command from CSV file.

Either way, you're going to receive "Differing mail hosts" error when trying to add users with the same email domain to any additional email config to the first one (usually the default email config org). This is happening due to some nuances of how Postini's Delivery Manager works and it's beyond the scope of this article (I'll write a separate post on logic of Delivery Manager as it also hides many pitfalls and gems as well).

To get rid of the error (and to allow the distribution of users across multiple email configs), you'll need to contact Postini support and ask them to "enable Wide Account flag" for your organization. It almost sounds as a secret code, isn't it? ;)

It takes seconds after support will provision the flag for you and - 'voilĂ ', - your configurations starts to work just as you expected. 

However, there is one thing you should be aware of: your backend configuration must allow internal routing between your email servers. 

This is because if a single email will be sent from outside to both and (while those users belong to different email configs) and the Email Config 1 (London) will be unable to deliver the email to you're going to experience another kind of error "Recipients not all at same mail host - psmtp", - but this is a good reason for another post ;)

Reference information for this post can be found here. Thanks to FrankM for pointing me out to this.
AuthorVadim Solovey
Categoriespostini, tips