Either when you’re trying to add a user account from a different domain to a SharePoint site collection or using People Picker you get a “no exact match found”.
The service account attached to the Sharepoint Web Application is used for user account verification. In the case where there is only a one-way trust between the domains, a login for the requested domain is required. For example, when you add a user from a different domain to the security list for a file, where the current login does not have permissions to the queried domain a login popup appears. Since a login dialog doesn’t appear for Sharepoint, an additional login is required.
In a multi forest network, separate logins will have to be registered against each domain. Assuming you have a login with permissions to the domains that are found in different forests you can run the following command on the Sharepoint server to register the login password (domain:<domain>, login, password; domain<domain>, login, password):
stsadm.exe -o setproperty -url "<https://SharepointPortal>" -pn "peoplepicker-searchadforests" -pv "domain:na.aecomnet.com,na\mosssp,Password; domain:as.aecomnet.com,nas\mossspas,Password; domain:corp.aecomnet.com,aecom/mossspcorp,Password; domain:au.aecomnet.com,au\mosstest,mos5test"