Gmail again!

[#1]

Here we go again!

Tried to email a friend on their personal Gmail address. No joy - returned by Gmail "To protect our users from spam, 421-4.7.28 mail sent from your domain has been temporarily rate limited." Had to email it to their work address - Delivery Receipt confirms as delivered.

What is this all about with Gmail and Plusnet?

Reporting-MTA: dns; gateway1.enmail.co
X-Postfix-Queue-ID: 5F87C4122C
X-Postfix-Sender: rfc822; ******@<User>.plus.com
Arrival-Date: Sun, 14 Jun 2026 12:42:06 +0000 (UTC)

Final-Recipient: rfc822; ******@gmail.com
Original-Recipient: rfc822;******@gmail.com
Action: failed
Status: 4.7.28
Remote-MTA: dns; alt1.gmail-smtp-in.l.google.com
Diagnostic-Code: smtp; 421-4.7.28 Gmail has detected an unusual rate of mail originating from your SPF 421-4.7.28 domain [<User>.plus.com 35]. To protect our users from spam, 421-4.7.28 mail sent from your domain has been temporarily rate limited. For 421-4.7.28 more information, go to 421-4.7.28 https://support.google.com/mail/?p=UnsolicitedRateLimitError to 421 4.7.28 review our Bulk Email Senders Guidelines.
38308e7fff4ca-39929c12a8dsi25113511fa.13 - gsmtp

My email 'domain' is <User>.plus.com - so the real underlying domain here is plus.com and this seems to be where the problem is.

--------------------------------------------
https://mxtoolbox.com/SuperTool.aspx

spf: plus.com

Test Result

Status Problem SPF Record Published No SPF Record found

Related Tests Result

Status Problem DMARC Record Published No DMARC Record found
Status Problem DMARC Policy Not Enabled It is recommended to use a quarantine or reject policy. To enable BIMI, it is required to have one of these at 100%.
------------------------------------------------

And yet, for me...

------------------------------------------------
spf:<User>.plus.com

v=spf1 include:_spf-internal.plus.net include:_spf-internal2.plus.net include:spf.greenby.com ~all
Prefix Type Value PrefixDesc Description
v spf1 The SPF record version
+ include _spf-internal.plus.net Pass The specified domain is searched for an 'allow'.
+ include _spf-internal2.plus.net Pass The specified domain is searched for an 'allow'.
+ include spf.greenby.com Pass The specified domain is searched for an 'allow'.
~ all SoftFail Always matches. It goes at the end of your record.

Test Result
Status Ok SPF Record Published - SPF Record found
Status Ok SPF Record Deprecated - No deprecated records found
Status Ok SPF Multiple Records - Less than two records found
Status Ok SPF Contains characters after ALL - No items after 'ALL'.
Status Ok SPF Syntax Check - The record is valid
Status Ok SPF Included Lookups - Number of included lookups is OK
Status Ok SPF Recursive Loop - Nor Recursive Loops on Includes
Status Ok SPF Duplicate Include - No Duplicate Includes Found
Status Ok SPF Type PTR Check - No type PTR found
Status Ok SPF Void Lookups - Number of void lookups is OK
Status Ok SPF MX Resource Records - Number of MX Resource Records is OK
Status Ok SPF Record Null Value - No Null DNS Lookups found

Related Tests Result
Status Problem DMARC Policy Not Enabled It is recommended to use a quarantine or reject policy. To enable BIMI, it is required to have one of these at 100%. Information More Info
Status Ok DMARC Record Published DMARC Record found
dns lookup smtp diag blacklist http test dns propagation
Reported by ns1.plusnet.co.uk on 6/14/2026 at 11:52:32 AM (UTC -5), just for you.
------------------------------------------------

Is the Gmail system getting confused between the senders IN the domain and the domain itself? I mean, I am rarely sending out any emails from <User>.plus.com but, obviously, there must be tons of emails coming FROM plusnet.com - whether SPAM or not!

I am going to contact Mr Google again. Which, after all, was the suggested approach in the polite message sent back from the Greenby email host.

[#2]

I suspect, but could be wrong of course, that now Plusnet (and others) have amended their protocols to line up with the non-mandatory elements of Gmails restrictions, they (Gmail) have moved the goalposts -again.

[#3]

Which SMTP server did you use ?

[#4]

...Delivered! (To 'Mr Google')

But, as before, I doubt I will be hearing anything constructive back.

[#5]

Since we're having trouble pinning down the specific SMTP configuration settings,
I'm going to step aside and let others chime in.

[#6]

@pvmb I don't know if this 'trick' still works, but have you tried (@googlemail.com ) rather than (@gmail.com)?

[#7]

---

@PhilipHeyes wrote:

Which SMTP server did you use ?

---

Take your pick!

mail.enmail.co [91.204.208.195] - An Enix Ltd IP address (Probably this)

gateway1.enmail.co [213.5.176.100] - An Enix Ltd IP address

[#8]

One possible explanation could be that there IS a lot of SPAM coming from Plusnet email addresses...

Some people who have complained of receiving a lot of SPAM over recent months have said some came from their own email address. Then again, some of the more dodgy 'recommendations' on here about the settings for client email software make me wonder if some people's Plusnet account passwords have been compromised, not just their email addresses.

[#9]

Skip the Ad! This comes from a commercial company with something to sell and seems intended for bulk email senders (Spammers?) but gives some insight. Whether useful of not is another matter.

https://www.suped.com/learn/email-deliverability/why-is-gmail-deferring-mail-with-421-4728-unusual-r...

Why is Gmail deferring mail with '421 4.7.28 unusual rate of mail' and sending it to spam?

"Gmail is deferring mail with 421 4.7.28 because it sees an unusual rate of mail tied to your sending identity. That identity can be the sending IP, IP netblock, SPF domain, DKIM domain, URL domain, or message pattern. When nothing changes after the warning, Gmail often has enough negative or weak feedback to move later mail to spam instead of simply slowing it down."

[#10]

As you say, @pvmb , that article is aimed at bulk senders, and does not really apply to private individuals. As I only really have one GMAIL/Googlemail contact, and use Mythic Beasts for email these days anyway, I am unable to really comment on what is/isn't happening, but we used to correspond quite happily when I was using the PN mail platform.

[#11]

A message sent earlier today to the same Gmail recipient has now reported as 'Delivered'. Let's hope this is a permanent change.

https://community.plus.net/t5/Email/Greenby-email-now-with-DKIM/td-p/2049076

[#12]

30/6/2026 13:58

Certainly not fixed today....   I tried twice... same result, all the gmail addresses have been bounced 

Diagnostic-Code: smtp; 421-4.7.28 Gmail has detected an unusual rate of mail
    originating from your SPF 421-4.7.28 domain [<....>.plus.com      35].
    To protect our users from 421-4.7.28 spam, mail sent from your domain has
    been temporarily rate limited. 421-4.7.28 For more information, go to

[#13]

@offscotland 

"30/6/2026 13:58

Certainly not fixed today....   I tried twice... same result, all the gmail addresses have been bounced"

Just sent an email to a GMail account - been successful previously.

<********@gmail.com>: host alt1.gmail-smtp-in.l.google.com[192.178.213.26]
said: 421-4.7.28 Gmail has detected an unusual rate of mail originating
from your SPF 421-4.7.28 domain [<User>.plus.com 35]. To protect our
users from spam, 421-4.7.28 mail sent from your domain has been temporarily
rate limited. For 421-4.7.28 more information, go to 421-4.7.28
https://support.google.com/mail/?p=UnsolicitedRateLimitError to 421 4.7.28
review our Bulk Email Senders Guidelines.
a640c23a62f3a-c1288d85613si193275366b.19 - gsmtp (in reply to end of DATA
command)

Nothing has changed at 'my' domain <User>.plus.com AFAIAC - I am certainly not sending either SPAM or frequent emails. So again, it can not be from 'my' domain but from plus.com Yet it quotes 'my' domain...

It's very frustrating to keep on seeing this nonsense. Are they actually getting SPAM or any frequent emails from 'my' domain - how do I know? If it's simply the total emails from plus.com (so why quote 'my' domain?) why has this not been sorted out by now?

[#14]

Ah! So what's this?

https://mxtoolbox.com/SuperTool.aspx#

blacklist:<User>.plus.com

Checking <User>.plus.com which resolves to ***.***.***.*** against 68 known blacklists...
Listed 1 times with 2 timeouts
                                                                                            
Status Problem LISTED

Blacklist:  ZEN    

Reason:  ***.***.***.*** was listed {Reason}

TTL:  300

 ResponseTime:  19 -  Ignore

Can't see Reason without registering for an account...

But, checking my 'domain' directly with Spamhaus gives: "<User>.plus.com has no issues"

BUT, checking my IP for my 'domain' directly with Spamhaus gives: "***.***.***.*** has 1 listing"

"Please don’t be alarmed! We understand finding your IP address, domain, URL or ASN on a blocklist can be worrying. This website will give you information about why you are listed and what you can do to ensure you don’t get listed again.

Where it is possible to request removal, we will help you through the process. However, if your IP is listed on the Spamhaus Blocklist (SBL), removal can only be requested by your Internet Service Provider (ISP)."

Policy Blocklist (PBL) - This is for information only. No action is required (unless you run your own mail server).
This IP is listed on the Policy Blocklist (PBL)

Don’t panic!
The inclusion of your IP address on the Policy Blocklist (PBL) is standard for the vast majority of internet users and is not the result of your actions*. Here are some key PBL facts for your understanding:

• If the IP address you are using is on PBL, you can still send email if you are using SMTP auth.

• You do not need to request removal from PBL.

• Listings on this blocklist are controlled by either your Internet Service Provider (ISP) or Spamhaus. Click on More Info for further details.

• PBL contains ranges of IP addresses that shouldn’t be sending email directly to the internet.

• Typically, IPs of broadband or dial-up customers will be included in this list.

• This is part of Internet best practices enacted to protect all users.

Run your own mail server?
If you run your own mail server, and require removal from the PBL, please click on “More Info” to review your ISP’s policy. Once you have reviewed the policy, please tick the “I am running my own mail server” check-box at the bottom of the page to enable removal.

NOTE: Exclusions are only valid for 1 year unless the ISP sets a more restrictive policy. If your IP gets listed on another Spamhaus Blocklist, it will automatically be relisted on the PBL.

So... My 'domain' is OK. But the IP for my 'domain' is not. And I am on a static IP!

This is starting to sound ridiculous to me and likely more to do with faults in whatever are the current Internet arrangements and functions for this than anything real to do with me. What do others think?

* Gee! So nothing I have done then? Note the use of the words "range" and "ranges" below:

***.***.***.***/** is listed on the Policy Block List (PBL)

Outbound Email policy of Plusnet Plc for this IP range
It is the policy of Plusnet Plc that unauthenticated email sent from this IP address should be sent out only via the designated outbound mail server allocated to Plusnet Plc customers. To find the hostname of the correct mail server to use, customers should consult the original signup documentation or contact Plusnet Plc Technical Support.

Removal procedure
If you are not using normal email software, BUT instead are running a mail server AND you are the owner of a Static IP address in the range ***.***.***.***/** AND you have a legitimate reason for operating a mail server on this IP THEN you can automatically remove (suppress) your static IP address from the PBL database.

About The PBL
The Spamhaus Policy Block List (PBL) is an international anti-spam system maintained by The Spamhaus Project in conjunction with Internet Service Providers and is used by Internet networks to enforce inbound email policies. The PBL database lists end-user IP address ranges which should not be delivering unauthenticated email to any mail server except those provided for specifically for that customer's use. The PBL lists only IP addresses (not domains or email addresses).

For full information on how the PBL operates please see the PBL Home page and the PBL Frequently Asked Questions.

So... It isn't ME, it's other Plusnet email account holders, in the same IP block as my static IP! ☹️

[#15]

...Thinks: Could rDNS lookup be involved here?

Like others, in the past I asked Plusnet to alter the original record for reverse DNS lookup on my account (for the usual reason). Now I am wondering... How come my named 'domain' is CLEAN but my static IP (of my 'domain') is on a block list?