The agent is sending the mail as you, because you're the one who created the agent - and it runs as you.
I have quite a few agents that run on schedule and send mails - what I did was to create a user named 'Automated Message/<mydomain>', add them to the ACL of the databases as well as the security section of the server docs, and finally to the 'Run on behalf of' field of my agents.
Then when the agent runs, it is sent from 'Automated message' - no confusion.
A similar, alternate idea might be that if you created a 'Notes Administrator' ID, run the agents on behalf of that user.
Sending Scheduled Emails Using Lotu... (Walter O Oriaro... 3.Apr.12)
Feedback response number WEBB8SZHTQ created by Mark Taylor on 04/03/2012
. . 'Run on Behalf of'.... (Mark Taylor 3.Apr.12)
. . PRINCIPAL (Paul K Smerdon 3.Apr.12)