hello, I am running Exchange 2010 and client is Outlook 2013. I have a shared mailbox which is used by department users to reply on behalf of Sales. I have granted "Manage Full Access Permission" to these users and also added them "Send on Behalf of" in the Delivery options. Still when they use this email account in the "From" field to send out a reply, they get a NDR stating they do not have permission to send on behalf of this user. Strange thing is it always works the first time they send an email using the "from", but fails everytime afterwards. Another strange thing thing is that if they select "other email address" and select Sales from the address list, the mail is delivered without any issue.
Is there something I am missing or doing wrong.