How do I permit a range of addresses for smtp

[ilpadrino]

I'm overlooking something in my access-list. Can someone give me a hint for allowing a range of ip addresses to send mail to my host. The range listed on the sender's instructions is:
a.b.0.0/20 (a.b.0.0 mask 255.255.240.0)

I added this to our router, but it's not working:
access-list 104 permit tcp a.b.0.0 0.0.240.255 host w.x.y.z eq smtp

Thanks.

 

[lgarner]

I know it's obvious, but is the access list applied to an interface? What's the rest of the access list look like?

 

[ilpadrino]

Yes, it's applied to the serial0.1 int which connects to the internet.

 

[lgarner]

Well, the rest of the acl would still be helpful. I assume that you mean that you have

interface serial 0.1
ip access-group 104 in

Another question is whether NAT is involved. Is "w.x.y.z" a public or private address?

 

[ilpadrino]

w.x.y.z is a public address. yes we use NAT.
i think i may have figured it out. i'm testing email right now. i may have entered the wildcard bits wrong.
i've change to

access-list 104 permit tcp a.b.0.0 0.0.15.255 host w.x.y.z eq smtp