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.