Comcast overview

Comcast was founded in 1963 and has two primary businesses: Comcast Cable and NBC Universal. Over the past 50 years, Comcast increased its business footprint in the U.S. and is the largest U.S. cable provider with more than 25 million email subscribers. 



North America; U.S. 



Suggested mail transfer agent (MTA) settings:

  • 25 simultaneous connections per sending IP address
  • 100 recipients per message
  • Comcast only allows 1000 messages an hour per netblock for senders using IPv6

Feedback loop (FBL) application 

Feedback Loop

Postmaster site



Return Path partnership with Comcast

In partnership with Return Path, Comcast uses the Return Path Certification whitelist for preferential treatment to Comcast email customers. Comcast also uses your sending reputation based on Return Path’s Sender Score and authentication results to determine your rate limit.

Comcast delivery mediation

Comcast has a public escalation process  to remove blocks.

Return Path guidance

Return Path understands Comcast well and may have data to diagnose deliverability issues.


Was this article helpful?
0 out of 0 found this helpful
Have more questions? Submit a request