Bulk email

I do not use outlookExpress or ThunderBird or any email program.
I only use Yahoo mail.
Also I never open anything in Bulk that is not from someone I know. My Anti-virus does not have a mail scanner. Do I need one?
Thanks Rocko.I sent a PDF to myself as an Attachment,and Yahoo,says they run it past Norton. But I normally look at attachments like
irrate death adders,and just dont open them.