# Comcast not accepting mail

**URL:** <https://discourse.mailinabox.email/t/comcast-not-accepting-mail/12377>\
**Category:** Help with Unusual Circumstances\
**Created:** [October 3, 2024, 7:11pm UTC](https://discourse.mailinabox.email/t/comcast-not-accepting-mail/12377 "2024-10-03T19:11:02Z")\
**Posts on this page:** 11\
**Page:** 1

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**Author:** ![zoof](https://discourse.mailinabox.email/user_avatar/discourse.mailinabox.email/zoof/32/231_2.png) [@zoof](https://discourse.mailinabox.email/u/zoof)\
**Post date:** [October 3, 2024, 7:11pm UTC](https://discourse.mailinabox.email/t/comcast-not-accepting-mail/12377/1 "2024-10-03T19:11:02Z")

</div>

Recently, Comcast/Xfinity stopped accepting mail from my MIAB instance. I am clean on Spamhaus so they must maintain their own blocklist or else they use another service. There are no instructions on how to remediate this. Has anyone else run into anything similar? Any ideas on how I can get this fixed?

```auto
Reporting-MTA: dns; box.example.com
X-Postfix-Queue-ID: B643C400CC
X-Postfix-Sender: rfc822; user@example.com
Arrival-Date: Thu, 3 Oct 2024 11:06:32 -0400 (EDT)

Final-Recipient: rfc822; user@comcast.net
Original-Recipient: rfc822;user@comcast.net
Action: delayed
Status: 4.0.0
Remote-MTA: dns; mx1a1.comcast.net
Diagnostic-Code: smtp; 554 resimta-a2p-652305.sys.comcast.net
    resimta-a2p-652305.sys.comcast.net ESMTP server not available
Will-Retry-Until: Sat, 5 Oct 2024 11:06:32 -0400 (EDT)

```

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<div class="post-metadata">

**Author:** ![vele](https://discourse.mailinabox.email/letter_avatar_proxy/v4/letter/v/e5b9ba/32.png) [@vele](https://discourse.mailinabox.email/u/vele)\
**Post date:** [October 3, 2024, 10:36pm UTC](https://discourse.mailinabox.email/t/comcast-not-accepting-mail/12377/2 "2024-10-03T22:36:41Z")

</div>

Please run ` cat /var/log/mail.log | grep "postfix/smtp" | grep -P 'status='`  
And report back the message you recieve when sending to comcast.  
Do you have rDNS enabled? Read here [554 Email Bounce Back Error Message Troubleshooting - Xfinity Support](https://www.xfinity.com/support/articles/fix-a-554-error)

---

<div class="post-metadata">

**Author:** ![zoof](https://discourse.mailinabox.email/user_avatar/discourse.mailinabox.email/zoof/32/231_2.png) [@zoof](https://discourse.mailinabox.email/u/zoof)\
**Post date:** [October 3, 2024, 10:58pm UTC](https://discourse.mailinabox.email/t/comcast-not-accepting-mail/12377/3 "2024-10-03T22:58:54Z")

</div>

Here is one sample entry:

```auto
Oct 3 18:11:58 box postfix/smtp[950079]: 747E741AD1: to=<user@comcast.net>, relay=mx2h1.comcast.net[96.102.157.180]:25, delay=71793, delays=71788/0/5.2/0, dsn=4.0.0, status=deferred (host mx2h1.comcast.net[96.102.157.180] refused to talk to me: 554 resimta-h2p-561807.sys.comcast.net resimta-h2p-561807.sys.comcast.net 123.234.111.222 found on one or more DNSBLs, see https://postmaster.comcast.net/smtp-error-codes.php#BL000010)

```

And yes, reverse DNS is correctly configured:

```auto
Reverse DNS is set correctly at ISP. [111.222.123.234 / 1111:2222::3333:4444:5555:6666 ↦ box.example.com]

```

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<div class="post-metadata">

**Author:** ![vele](https://discourse.mailinabox.email/letter_avatar_proxy/v4/letter/v/e5b9ba/32.png) [@vele](https://discourse.mailinabox.email/u/vele)\
**Post date:** [October 3, 2024, 11:05pm UTC](https://discourse.mailinabox.email/t/comcast-not-accepting-mail/12377/4 "2024-10-03T23:05:12Z")

</div>

> [@zoof](#):
>
> ` DNSBLs,`

Check yourself here [MultiRBL.valli.org - Blacklist, Whitelist and FCrDNS check tool](https://multirbl.valli.org/lookup/) and try to delist yourself from as many as possible. They might be running their own blacklist ruther than Spamhaus. and try to delist yourself from as many as possible. They might be running their own blacklist rather than Spamhaus.

EDIT sorry here is the error: BL000010

[https://spa.xfinity.com/postmaster?faq=comcast-mail-errors](https://spa.xfinity.com/postmaster?faq=comcast-mail-errors)

Delist yourself from here: [CSI IP Reputation Remediation Portal](https://csi.cloudmark.com/en/reset/)

And now I remember that I successfully delisted myself from there once.  
Just explain that you are not sending unsolicited mail.

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<div class="post-metadata">

**Author:** ![zoof](https://discourse.mailinabox.email/user_avatar/discourse.mailinabox.email/zoof/32/231_2.png) [@zoof](https://discourse.mailinabox.email/u/zoof)\
**Post date:** [October 4, 2024, 12:53am UTC](https://discourse.mailinabox.email/t/comcast-not-accepting-mail/12377/5 "2024-10-04T00:53:14Z")

</div>

Thanks!

It’s so frustrating that IP addresses that have been clean for so many years get periodically listing on various block lists. It’s such a pain to self host email these days that I wonder how much longer I can do this.

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<div class="post-metadata">

**Author:** ![vele](https://discourse.mailinabox.email/letter_avatar_proxy/v4/letter/v/e5b9ba/32.png) [@vele](https://discourse.mailinabox.email/u/vele)\
**Post date:** [October 4, 2024, 9:08am UTC](https://discourse.mailinabox.email/t/comcast-not-accepting-mail/12377/6 "2024-10-04T09:08:53Z")

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> [@zoof](#):
>
> It’s such a pain to self host email t

I do agree. There have been a number of users on this forum who have moved to other commercial servers for these reasons.  
@JoshData  
I wander if the greeting ` ESMTP Hi, I'm a Mail-in-a-Box (Ubuntu/Postfix; see https://mailinabox.email/)` can get you on the non-public lists such as this one? Is there any other telltale sign which can identify a self hosted MIAB to these overzealous blacklist maintainers?  
As far as I know this could be edited in main.cf and thus may trick them into thinking that the server is not self-hosted.  
Is there a way to check the current number of active MIAB servers?

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<div class="post-metadata">

**Author:** ![zoof](https://discourse.mailinabox.email/user_avatar/discourse.mailinabox.email/zoof/32/231_2.png) [@zoof](https://discourse.mailinabox.email/u/zoof)\
**Post date:** [October 4, 2024, 1:38pm UTC](https://discourse.mailinabox.email/t/comcast-not-accepting-mail/12377/7 "2024-10-04T13:38:46Z")

</div>

I think the problem is that list maintainers frequently add entire blocks of IP address that have been the source of suspicious emails, regardless of individual IP address reputations. And then of course there are the conglomerates like Google and Microsoft for whom it is in their interest to make self hosting difficult to force people onto their platforms.

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<div class="post-metadata">

**Author:** ![jlangford02](https://discourse.mailinabox.email/letter_avatar_proxy/v4/letter/j/dc4da7/32.png) [@jlangford02](https://discourse.mailinabox.email/u/jlangford02)\
**Post date:** [October 5, 2024, 11:06pm UTC](https://discourse.mailinabox.email/t/comcast-not-accepting-mail/12377/8 "2024-10-05T23:06:01Z")

</div>

If the mta is correct then thte domain could be why you are being blocked

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<div class="post-metadata">

**Author:** ![JoshData](https://discourse.mailinabox.email/user_avatar/discourse.mailinabox.email/joshdata/32/2153_2.png) [@JoshData](https://discourse.mailinabox.email/u/JoshData)\
**Post date:** [October 7, 2024, 10:14am UTC](https://discourse.mailinabox.email/t/comcast-not-accepting-mail/12377/9 "2024-10-07T10:14:24Z")

</div>

> [@vele](#):
>
> I wander if the greeting ` ESMTP Hi, I'm a Mail-in-a-Box (Ubuntu/Postfix; see https://mailinabox.email/)` can get you on the non-public lists

I don’t think that’s the cause.

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<div class="post-metadata">

**Author:** ![vele](https://discourse.mailinabox.email/letter_avatar_proxy/v4/letter/v/e5b9ba/32.png) [@vele](https://discourse.mailinabox.email/u/vele)\
**Post date:** [October 7, 2024, 10:19am UTC](https://discourse.mailinabox.email/t/comcast-not-accepting-mail/12377/10 "2024-10-07T10:19:18Z")

</div>

I just edited the main.cf message and immediately got a bounce from gmail. They might also filter according to the greeting message provided that there are spammers using MIAB.

[ristotodov@gmail.com](mailto:ristotodov@gmail.com): host [gmail-smtp-in.l.google.com](http://gmail-smtp-in.l.google.com)[173.194.76.27] said:  
550-5.7.1 [141.22.32.217 12] Gmail has detected that this message is  
likely 550-5.7.1 unsolicited mail. To reduce the amount of spam sent to  
Gmail, this 550-5.7.1 message has been blocked. For more information, go to  
550 5.7.1 [Why has Gmail blocked my messages? - Gmail Help](https://support.google.com/mail/?p=UnsolicitedMessageError)  
ffacd0b85a97d-37d1695e25dsi2266351f8f.289 - gsmtp (in reply to end of DATA  
command)

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<div class="post-metadata">

**Author:** ![Ozfer](https://discourse.mailinabox.email/letter_avatar_proxy/v4/letter/o/6de8d8/32.png) [@Ozfer](https://discourse.mailinabox.email/u/Ozfer)\
**Post date:** [October 12, 2024, 2:18am UTC](https://discourse.mailinabox.email/t/comcast-not-accepting-mail/12377/11 "2024-10-12T02:18:48Z")

</div>

I am also being blocked by comcast it just keeps saying my emails are being throttled. To be fair google is also blocking me. Yahoo/ATT used to block me but I think I manually got off their blocklist.