Michael Hafen <mdhafen@tech.washk12.org>
  

I don't have a preference either way.  However it seems that being able
use an external SMTP server is a big deal.  So I will start by voting
for Mail::Sender and C4::Mail
    

Using an external SMTP server is a big thing. It requires a lot of extra
error handling to avoid losing mail, because SMTP servers need not accept
email  when koha wants to send it. A local sendmail is safer in that way.
How does this C4::Mail handle getting 4xx or 5xx replies?

Thanks,