Can't send Email to the same address too often

[#1]

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@Townman wrote:

@balvack2 

Which email client is that?

The server names are correct, but port numbers and encryption are not shown.  One will just have to hope that the client's guess work is correct!

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It's Mac mail v12.4

And if I understand your earlier post correctly the client has guessed port 465 or port 456?

[#2]

@plusnettony, @Townman 

This error has reappeared!  I got it a few mins ago, i.e. just before 19:00 but it went without error at 19:02.

[#3]

Thank you for the details. I'll do some testing and report into the office tomorrow (assuming it's not already raised).

[#4]

@plusnettony Has any progress been made with this problem?

It happened to me yet again at 16:48 today, but email went ok at 17:00.

This seems yet another problem that has been going on for weeks now!

[#5]

This problem is still happening to me, and it is very annoying! Is anyone else still suffering?

My first email today was sent at 11:39, but failed with 452 error. Worked ok at 12:00:10

It was to a single address, sent from my Force9 address to relay.force9.net port 587 using StartTLS witrh no VPN.

@plusnettony Now that other major email problems seem to be resolved, please can this be looked at?

[#6]

@mavison 

This is not widely reported since the August Bank Holiday weekend and that was on Plusn.com.

For avoidance of doubt, what does relay.force9.net resolve to for you please.

I have not been able to reproduce this on a test account.  If it helps any I could send you a cURL test to send an email from the terminal window.

[#7]

Still happening for me too (e.g. yesterday evening).

ping relay.force9.net

Pinging mail.force9.enmail.co [91.204.208.196] with 32 bytes of data:

[#8]

ping relay.force9.net

gives

PING mail.force9.enmail.co (91.204.208.196)  56 data bytes

Is that sufficient?

[#9]

Yes that confirms that you are pointing at the right service.

[#10]

Re the 452 too many emails error - as far as I can see, it's intermittent and on a Force9 address, is that correct?

[#11]

Yes.

[#12]

Yes, it is from a Force9 address.

As for intermittent, I suspect maybe not. I normally do not send many emails, so i may only notice it occasionally. As a test of that, yesterday at 16:46 i started a routine that tried to send an email every 5 minutes - assuming that 12 in an hour should be acceptable. I had failures at 16:56, 17:41, 18:41, 19:46, 20:41. In each case the send the failures continued up to the hour, but sending at xx:01 worked fine. I have just started it again at 09:46, and it failed at 09:51, but the send at 10:01 worked. That looks nore like consistent failures to me!

[#13]

I'm back! So is the issue could not send at 9:55 - OK at 10:01

Been alright since 13 September 2025

[#14]

@mavison 

That is a precise profile of the volume limiting mechanism - the metric is reset on the hour.  At some point in the hour, the permitted allowance becomes fully utilised and then no more emails may be sent.

@plusnettony 

This has the same experience profile as that seen with *.plus.com users on the late August BH weekend when relay.plus.com was switched to the Greenby proxy server.  The mitigation at that time was to raise the quota … which I suspect led to the deluge of spam proliferation and all the consequences which followed.

That experience seemed to infer that the Greenby proxy hand off back to the PN SMTP treated the proxy as a single submitter as far as volume limiting is concerned, not the actual user however that is determined (from address or sending IP address).

Force9 has been on the Greenby proxy for many weeks with no apparent issues.  Has the volume of Force9 mail increased significantly over those weeks leading this brand now encountering the same issue which plus.com users saw in August after which relay.plus.net was reverted to the PN servers.

From the outside looking in, it appears that when the SMTP service used is Plusnet’s via the Greenby proxy, the volume counting mechanism cannot discern individual users.  It’s a bit like Microsoft treating all *.plus.com as a SINGLE user for bulk mail volume counting.

That characteristic has now bitten Force9 … is there a noticeable increase in spam generation in the domain? 

[#15]

@Townman. I agree with your last post - except I have suffered from 452 errors since August as well!  See my initial post in this thread on 20/08/2025.

Tests today show similar failure patterns so far - except that 10am to 11am posts all worked!