Hi Amreek, as Michal mentioned, this did not solve our problem. To sum up the situation.
we have a user "CRMadmin", who is an administrator in CRM and has enabled "allow other users to send email on my behalf" and "Allow e-mail user to use my credentials to send message" with filled credentials to. This user has mailbox in Exchange 2010
This user is set in e-mail router to authenticate to the CRM server.
Then we have the user "CRMMail", who is not in CRM and has mailbox in Exchange 2010. This account has granted "Send As" permission. This account is set as described in the first post.
Customer is using Exchange 2010 and following commands has been run
New-ManagementRoleAssignment –Name: "CRM Email Router” -User: "crmmail@ORG.com" –Role:"ApplicationImpersonation"
Add-MailboxPermission -Identity "CRM Admin" -User crmmail -Accessright Fullaccess -InheritanceType all
when I try to send an e-mail message from CRMadmin from CRM to any e-mail address then we get the mentioned error. Once we grant the delegate rights then it is sent on behalf.
Milan