Error Cannot open mailbox

[MrThomas]

Hi wonder if somebody could help me.....

I have just taken over the I.T and have found there is this bit of software running on the server and it errors with the following

Cannot open Mailbox (then the name of user) Ensure the Archive service user (then the name of thi account).

then the error message also has

Archive Service
Cannot open mailbox (then the users name) Ensure the Archive Service user 'Archive@.com' has permissions to open this mailbox, the Exchange information store is running, and Active Directory is running correctly.

Now nothing has changed and i know this did work!!!!

the user has permissions but now i am stuck....

Can you help please