There is no "dead letter office" for email. If you are considering canceling your Comcast Internet service, the ultimate destination of your email depends on what email address you use. The steps needed to preserve your access to your email are based on what Internet provider, if any, you choose for your future Internet access.
For Comcast Addresses
The destination of your email hinges on whether you use the email address that Comcast made available to you when the service was first installed. For instance, if you use "email@example.com," your friends will receive "undeliverable" messages the first time they email you following your service cancellation, unless you notify them beforehand of your new email address.
Other Paid Providers
If you plan to adopt another paid provider for your Internet service and use its name as part of your email address -- "firstname.lastname@example.org" -- be sure to export and save your current contacts or obtain your new service and name first and email all your contacts with your new address.
Using Paid Providers
Changing to paid providers for your email service, and subsequently using their name as part of your email, means you must notify all of your contacts of this new provider you adopt. At one time, paid email providers provided more storage space, spam protection and legitimacy to you or your company's email address. This is no longer the case.
Free Email Providers
Hotmail, Yahoo and Gmail are all free email providers that make their money on site ad space tailored on either the title or content of your email messages. AOL has begun a free email account service as well. Some of these services have attained a respect and legitimacy that were not afforded early free options, and Gmail in particular is used by some companies. A huge advantage of adopting a free email address is that you can maintain and access your email independent of whatever company you choose to provide your Internet service.