If you have multiple mailboxes in your Outlook profile, you can configure Team Helpdesk agent add-in to track outgoing/incoming emails related to existing tickets from both primary and secondary mailboxes.
By default, Team Helpdesk Agent add-in only tracks and processes the emails associated with existing cases from your primary mailbox. So, if you use other accounts to reply to cases or if you receive emails from callers to other mailboxes in your Outlook, then you must specify those mailboxes under Team Helpdesk Agent > Outgoing Email Tracking and Team Helpdesk Agent > Incoming Email Tracking respectively. Enabling this would force your Team Helpdesk Agent add-in to look for incoming/outgoing emails in those mailboxes too.
Team Helpdesk Agent > Personal Settings > Email Tracking – Incoming
Team Helpdesk Agent > Personal Settings > Email Tracking – Outgoing
NOTE: If you and other technicians have opened the same mailboxes in Outlook, only one of you should enable Team Helpdesk Agent add-in to track those mailboxes. If multiple technicians have the same mailboxes tracked, it could generate Exchange conflicts to the cases.