I think you have to switch to a business class service with Comcast to 
get a static IP address that is really static.
What they might do if it isn't business class is a MAC reservation 
within the DHCP scope for an address, this would cause your mail to get 
bounced as a dynamic address. The address would still be in the scope 
that is dynamic.
They use the MAC address on your router and tell the scope the address 
associated with this MAC can't be given to any other MAC address.

Many businesses use reservations within a DHCP scope to keep from having 
static addresses on all their servers, it's easier to manage.

Sam.



Chris Schumann wrote:

>Hey all,
>
>I set up a Linux server at home, bought a domain name and have e-mail
>running on it pretty well. Sendmail and Cyrus-IMAP.
>
>However, I just sent something to someone on Lycos, and it was rejected
>because SORBS lists my IP address as being dynamic... which is correct.
>
>So now what? Is it the "right" thing to send my e-mail through my ISP
>(Comcast)? Do I *need* to masquerade when I do? Should I get a static IP?
>
>What do you folks do?
>
>Chris
>
>
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>