Joe:
For the forum to help you with this issue, we do need to know;
MAPI or Direct?
If MAPI, Outlook or other?
Exchange server?
Office 365? Cloud version?
Recently Office 365 doesn't like it when more than 30 emails in a minute are sent (I believe that is a new restriction). Not sure if this is what is causing the problem or not. If it is, the AR doesn't know how to deal with the error that Office 365 is kicking back, so it through up it's hands in frustration and reports an Access Violation error.
Another client has a similar issue with emailing PayDirt Pay Advices. We recommend trying a service called, smtp2go.com. We haven't tested this yet ourselves.