Xfinity (Comcast) to Yahoo Transition: What It Means for Email Senders & Deliverability Professionals

Starting in June 2025, Comcast’s email service (comcast.net) will be gradually phased out and replaced by Yahoo Mail. The transition is expected to continue through 2026, according to the official announcement.

While this might sound like just another backend change, it’s actually a pretty big deal for email senders, ESPs, and deliverability teams.

Why? Because it affects how your emails get delivered, tracked, and received, and it’s happening across millions of mailboxes.

Here’s what you need to know to stay ahead.

What Does This Transition Mean?

All @comcast.net email addresses will be gradually migrated to Yahoo Mail, allowing users to retain their existing comcast.net addresses.

The transition will be rolled out in phases, with affected users receiving a 30-day notice prior to their accounts being migrated.

Once a user accepts Yahoo’s Terms of Service and Privacy Policy, Yahoo officially takes over as the email provider for that mailbox, managing everything from delivery to filtering (including the spam folder).

Key Implications for Senders

If you’re wondering how this migration might affect your emails, here are the key takeaways to keep in mind.

1. Spam filtering will now follow Yahoo’s rules

Once a user migrates, Yahoo’s anti-spam and filtering systems take over. Expect different inbox placement behavior than you are accustomed to with Comcast.

Reputation and engagement history under Yahoo will now matter more.

2. No email forwarding

If your recipients were forwarding their Comcast emails elsewhere, that forwarding will stop after the migration.

Delivery errors may rise temporarily if users haven’t completed their transition or updated third-party clients.

3. Changed IMAP/SMTP settings

Once users switch to Yahoo Mail, they must update their third-party clients (such as Outlook and Apple Mail) with the new Yahoo settings.

If they don’t, your message/newsletter/survey, etc., may bounce or be undelivered during the transition period.

4. Sudden changes in deliverability and engagement metrics

As Comcast begins migrating its @comcast.net email addresses to Yahoo Mail, senders and email service providers (ESPs) should be aware of several risks that may impact deliverability and engagement.

One of the most immediate concerns is a sudden spike in bounce rates for Comcast.net addresses, especially during the switchover windows when users may not have completed the transition or updated their mail client settings.

In addition, senders may observe unusual drops in open rates, largely due to Yahoo’s more aggressive spam filtering algorithms, which differ from Comcast’s historical filtering behavior.

There’s also the potential for engagement delays, as some users may be temporarily locked out or experience difficulties reconfiguring access to their inboxes via third-party apps (such as Outlook or Apple Mail) after the migration.

What Should Senders and ESPs Do?

To stay ahead of potential issues, senders should take proactive steps.

Start by closely monitoring bounce messages from @comcast.net recipients. These may provide early signals of access or filtering problems during the transition.

Also, this is a great time to clean up your lists by suppressing long-inactive @comcast.net subscribers or triggering re-confirmation campaigns. Yahoo heavily weighs engagement in its filtering, so fresh consent and activity can make a difference.

What You Need to Know Before the Transition Begins

It’s important to note that only @comcast.net email addresses are affected by this transition; no other Comcast or Xfinity services are impacted.

There are also technical limitations to be aware of:

• Yahoo will only migrate up to 4,100 folders and 10,000 contacts per mailbox.
• Anything beyond these limits will be trimmed or consolidated.
• Email attachments larger than 25MB will not be migrated. That could affect archived content, re-engagement emails, or large support messages.

This migration is a big shift for senders who deal with comcast.net users.

While addresses remain the same, behavior, filtering, and expectations will change. Stay proactive, monitor engagement, authenticate your mail, and prepare for Yahoo’s inbox logic to take over.