Outlook starts at login

We have Norton Small Business on PCs.

PCs have started forcing Outlook to open when logging on.
We have MS Office, but do not use Outlook so there is no profile set up.
Took a bit of trial and error but found it was Norton trying to apply anti-spam.
Disabled the anti-spam in settings and this stopped Outlook being started.

Sure this is not just me so hope this helps.