I use define(`SMART_HOST',`[mail.bellsouth.net]') in sendmail.mc. This has been working well since long before FC2.
Why the Bellsouth SMTP server in squared brackets?
I haven't seen that done in SMART_HOST, but in mailertable the square brackets mean that the host is the actual SMTP host. Without them, sendmail does a DNS lookup on the name looking for an MX record, assuming that the name is an email domain, not a particular host.
