# Comcast

The Comcast Corporation, an American multinational telecommunications conglomerate, provides cable television and internet services including email.

To send to Comcast recipients depends on your sending reputation and following sending best practices. This doesn't guarantee inbox placement at Comcast, but increases your chances for success. Senders should avoid creating large, abnormal spikes in volume since Comcast might perceive these as spam.

> \[!NOTE]
>
> Comcast is migrating email users to Yahoo infrastructure gradually throughout 2026.

## Authentication support

Comcast supports, but doesn't require, SPF, DKIM, or DMARC. Comcast strongly encourages senders to implement all three. As the industry shifts to full authentication, senders should establish a DMARC policy.

## Blocklisting

Comcast accepts email based on its own internal blocklist and those of [Return Path][], [Spamhaus][], [Cloudmark][], and [Vade Secure][]. If any of these providers list your IP address, Comcast rejects your email.

## Feedback loop

Comcast routes complaints through the [Validity Feedback Loop (FBL)][fbl]. Twilio subscribes to the Validity FBL.

[fbl]: /docs/sendgrid/glossary/feedback-loop

[Return Path]: /docs/sendgrid/concepts/deliverability/blocklist-provider-insights#return-path

[Spamhaus]: /docs/sendgrid/concepts/deliverability/blocklist-provider-insights#spamhaus

[Cloudmark]: /docs/sendgrid/concepts/deliverability/blocklist-provider-insights#cloudmark

[Vade Secure]: /docs/sendgrid/concepts/deliverability/blocklist-provider-insights#vade-secure