[CentOS] postfix tightening

I am used to sendmail and am using Postfix now and am uncertain of some
features. I typically would comment out the line in sendmail.mc that
went something like 'accept unresolvable domains'

I tried using

smtpd_sender_restrictions =
       reject_unverified_sender
       reject_unverified_smtp

and this seems a bit too restrictive and got some bounces on legitimate
senders

so I'm thinking that this is perhaps a bit more apropos...

smtpd_helo_restrictions = 
	permit_mynetworks,
	reject_invalid_hostname

does this make sense?

Craig