After I add an Exchange account, inbox and outbox fill with hundreds of erroneous emails

Hi. Lately I added an Exchange account to retrieve and send work emails. After a slight hitch in the configuration the first time I tried (received an error message: Account cannot be added. Note that Outlook 2011 requires Exchange Server 2007 SP1 Update Rollover 4 or later), the account appeared to be added. Suddenly my inbox and outbox began to fill with ever-increasing numbers of an old vacation response which is NOT, repeat NOT set anywhere. Only want to stop was to delete the account. Also interesting, NONE of the incoming emails were actual work emails, only the vacation reply. Lastly, this is NOT happening when I add the account to my IPhone. I know there are issue with compatibility btw Outlook Mac and MS Exchange but how to resolve -- or not? We are a non-profit org; our "IT Manager" is a volunteer and therefore has limited time to work on this but I would like at least to forward him your reply to be helpful. Thanks!