The sendmail functionality uses an api called mapi. As this api is not
controlled by Acrobat it can be influenced by outside sources. This api
can be expoited by viruses etc for DOS attacks. for this reason many of
the virus scan software vendors have provisions in their software that
will affect when mapi calles can be made.As far as webmail is concerned
there is no api for that program (there is no automation) so it is
expected that the user will save the pdf and attach it to an email by
hand....