The best way to avoid security problems with sendmail is to avoid using it (at least directly). Postfix is a drop-in replacement for sendmail, which would allow you to get rid of it altogether.

There are a number of Perl modules available to send e-mail, from the very simple (Net::SMTP, to the effective (Mail::Sendmail), to the fully-equipped (MIME-Tools).

I tend to favour using Mail::Sendmail, which, despite its name, does not require the sendmail program (it just needs the hostname of a local MTA, which defaults to localhost), and is also pure Perl.