in which world do you live? Many if not most of the major ISPs reject mail
servers which do not have a PTR record. From the view of a customer this
makes a mail server without a PTR record wrongly configured, even if you do
not like this.
mediocrity is excellence at pursuing the mean. just because "major ISPs"
reject mail for bad reasons is not a justification for others to do so.
Stupid spam filtering mechanisms are a DoS attack on email.
Right, but this mechanism is not stupid, instead it is clever ;-)
nope. it makes no sense whatsoever. it is using a completely irrelevant test
to decide whether mail is legitimate. and it's easily defeated by spammers.
it's not only a complete waste of time, it's worse in that it causes legitimate
mail to be dropped.
rejecting mail for this reason should be a criminal offense.