Setting up reverse DNS correctly

[Craig L. Ching]

I recently had a sent e-mail to comcast.net bounced back to me saying
something about "only valid hosts may send."  Tracking it down, I
found (using www.dnsreport.com) that I might not have reverse DNS set
up correctly for my domain name.  Could somebody help me out with
this?  Here is the db file for the domain (unaltered).  The named
daemon is bind 9 (not sure of the exact version).

$TTL 86400
webasap.net. IN SOA sumo.webasap.net. cching.sumo.webasap.net. (
			2004071401	; Serial
			10800		; Refresh after 3 hours
			3600		; Retry after 1 hour
			604800		; Expire after 1 week
			86400 )		; Minimum TTL of 1 day
webasap.net. IN NS sumo.webasap.net.

;
; Host addresses
;
sumo.webasap.net.	IN A	67.107.38.61
www.webasap.net.	IN A	67.107.38.61

;
; MX records
;
webasap.net.			MX 0		sumo.webasap.net.

;
; Aliases
;
sumo.				IN CNAME	sumo.webasap.net.

I have tried a few things in the last couple of days, but haven't
gotten dns report to tell me it's set up right, so I've set it back
the way it was originally.  Thanks for any help and let me know if I
need to post any other information!

Cheers,
Craig