Is it possible to find the internet email address(es) that belong(s) to a user account or vice versa through GroupWise 8 soap calls?

The getUserListRequest returns a list of UserInfo objects, but the email field only contains the internal email address ([user name].[post office name].[root]). I've checked (almost) all of the requests, including getSettings and getAccounts, but reading up on those, it doesn't seem to have this information.

Could a combination of getCustomList with some other call be used for this or is it not possible and would I need to talk to the eDirectory directly perhaps?

Or is it possible to make the UserInfo.email field return the preferred email field or an alternative email format?

Thanks in advance.