Reverse Dns Question...is it really necessary or not?

Hi,

I have my own dns server using Bind 9.x. I have setup all the zones
for eacb of my domains! Here my question:

if no reverse dns are setup for my domains, is it possible that I may
miss couple of emails? Some of my friends or clients have often some
difficulties to send me emails (Mails strangely bounce)

I have an other question...does the reverse dns have to be setup on
the ISP server or on my dns server?

Thx all

--
Chris

Love has no law but the law of love