Hello Eric,
The email account you specify in "Tools>Manage Email Accounts>Email Account Settings" for your incoming email address doesn't have to be dedicated, but you may find that it's simply easier to manage your support emails that way. Using a personal email address, or even one that's used by other individuals or software, may create confusion and ultimately cost you more time and energy.
An email is flagged when an item is created from it in OnTime, and will ignore any emails that have already been turned into items.
I'm not sure exactly what you mean by adding subject masks to match an email, but I can tell you that OnTime will read the subject of incoming emails and look for an itemID. If OnTime finds an itemID inbetween brackets(such as in [#001234]) and there's an existing item in your database, instead of creating a new item OnTime will simply log that email under the existing item.
You can read more about configuring Email Accounts by searching for 'Email Accounts' in our Administrator's Guide.
Let me know if you have any further questions.
Thank you,
Tom Harder
Axosoft Support
support@axosoft.com1.800.653.0024 option 3--'Fear the Bug' Podcast--