I had to re-create my FIM Service Account since by mistake the user had been created as a mail contact and therefore didn't have a user mailbox. After having created the user and a mailbox and added it to the appropriate groups etc., deleted and re-created the user/login in SQL Server and re-configured the FIM Service DB and the FIMService Windows service, everything seems to be working fine - almost ... because when I request ie. a Distribution Group an approval workflow and email is generated, but when I open the mail in Outlook as the approver I receive the above error message ... and off course the approve/reject buttons are greyed out ...
by clicking on more info I receive the below:
"This request cannot be approved or rejected for the following reason(s):
The sender (FIM Service Component User) is not an authorized sender of approval requests.
Authorized sender of approval requests are:
Contact your system administrator for assistance."
'FIM Service Component User' is the display name of "srvc_fimservice" ...
I don't know where to look / change the mail sender ... my guess is that FIM still tries to use the SID of my previous FIM Service user ... btw I re-created the account with the exact same name as before.