Clarification on use of Sophos

[Brian Parish]

I have just installed MailScanner, so this is a question which can
probably be handled by saying RTFM.  Anyway, can someone clarify for me
the role that Sophos plays?  I suspect that without it, MailScanner can
be configured to strip attachments that seem to be executables, vbs
etc., but not to recognise virus signatures within these attachments.
Is that correct? i.e. Is MailScanner alone an effective virus/worm
control mechanism if all suspect attachment types are stripped?

TIA
Brian