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user_WT51
20th Anniversary celebration
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Monday, January 5th, 2026 1:56 AM

451 Errors

For the past few days, I’m receiving 451 errors from the Comcast email system when I send to xxxxx@comcast.net addresses from a yyyyyy@gmail.com account.  What can I do to resolve the issue?

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XfinityMatthew

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4 days ago

Hello @user_WT51 What specific errors are you getting? We also have a list of common email errors that explain the issue that can be found here: https://www.xfinity.com/support/articles/email-errors

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user_WT51

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4 days ago

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XfinityMatthew

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The "Too many messages for sender" error with Xfinity usually means you've hit our daily sending limits (around 1,000 emails/day) or a per-message recipient limit (around 100) the other cause could be Spam Filters: Sending many emails quickly, even if individually, can look like spam and get blocked. The block is often temporary; and usually resolved by waiting to the next day to send more.

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4 days ago

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user_WT51

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I have never sent more than a few emails a day. This has been going on for days, with several Comcast.net email addresses.  Gmail keeps trying to resend daily.  Could this be a bigger issue between Gmail and Comcast?

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4 days ago

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XfinityMatthew

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1.2K Messages

If there is one it's not one I'm aware of currently and nothing is being reported on our outage board. You can submit a ticket under the postmaster option at https://spa.xfinity.com/help to report the issue and have it get looked in to. 

I am an Official Xfinity Employee.
Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
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4 days ago

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user_WT51

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Ok, thanks I will file a report. 

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4 days ago

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TKDS

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4 Messages

1 day ago

I'm having this same exact issue.  It started on 12/29/25, and is still happening.  In my case, I am using Microsoft Outlook.  If I send emails using the Gmail app, my comcast recipients will receive the message.  But not if I use Outlook.  How can I get cleared from this blacklist?

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XfinityThomasA

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Hello, TKDS. Thank you for joining the Xfinity forums community for help. I know how frustrating that can be. You can report the problem directly to our specialists by submitting a ticket under the Postmaster option at: https://spa.xfinity.com/help

 

I am an Official Xfinity Employee.
Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Please, mark a reply as the Accepted Answer.tick

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1 day ago

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TKDS

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1 day ago

I submitted a report as suggested above.  I quickly got a message saying I am not blocklisted.  I do not receive error BL000000.  They say if I do not have that error, follow the link in my error, but there is none.  Please help.

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XfinityJustinM

Official Employee

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463 Messages

@TKDS, can you share with us the error that you are seeing without sharing any personal information? 

I am an Official Xfinity Employee.
Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Please, mark a reply as the Accepted Answer.tick

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1 day ago

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TKDS

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4 Messages

1 day ago

Same as WT51 above:

  • 451 4.2.0 (my gmail address) Too many messages for sender

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XfinityJustinM

Official Employee

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463 Messages

@TKDS ,
Would it be possible to remove the comcast.net addresses from the large grouping, and attempt to send out the email to that smaller subset? 

I am an Official Xfinity Employee.
Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Please, mark a reply as the Accepted Answer.tick

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1 day ago

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TKDS

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1 day ago

It comes with two attachments:  details.txt and Untitled attachment 03766.txt.  Those contain a lot of info, including the email addresses.  But these are from Google, not Comcast.

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