SMTP error 452 (too many recipients in the last hour)

[#1]

It is not *you* sending too many emails, it is all of '   *****.plus.net   ' sending too many emails, and a dumb attempt at a spam sending limiting function nobody wants to fix.

With or without the contribution from Greenby ?

The problem should solve itself soon enough given the dire behaviour of Greenby - there won't be enough users left to send 'too much' mail !

[#2]

That makes more sense. Thanks. Just tried a resend and my only outbound for today appears to have been successfully sent.

[#3]

My mother is sometimes getting SMTP error "too many recipients" even if she re-sends a failed email early in the new hour (eg xx:05). It's getting to the stage that it sometimes takes her three or four attempts to send an email, and requires her to monitor her inbox every time she tries to send to see if it's been bounced.

It seems to be a problem that is far more common with mmm@uuu.force9.co.uk addresses (ie using relay.force9.net) than with mmm@uuu.plus.com addresses (ie using relay.plus.net) (*). It doesn't help that it looks as if she's low down the list for migration to Greenby - maybe because she has a website and a domain that points to it. Mind you, migration to Greenby is not a universal remedy, given the periods when their POP server is rejecting connections from mail clients, as happened last night (3 March).


(*) I never saw it with my plus.com address / relay.plus.net before we were migrated to Greenby.

[#4]

@plusnettony I'm getting the Server error: '452 <xxxxxxx> recipient rejected - too many recipient in last hour'

I'm a force9 legacy customer and have not been migrated or been informed of a migrating but keep getting issues send mail from my PC Outlook client and Android mobile client. happened to day Sent: 05/03/2026 16:37

[#5]

The workaround for this error is to wait until just after the hour and resend then.  You should find the message will go without error.

[#6]

Having the same problems.  Email just not flowing, and when it does I'm being told it doesn't arrive.  Anything we can do to fix it.  Obviously, use an alternative email address/platform.  But I'd rather not.

[#7]

---

@KenCoggin wrote:

...Anything we can do to fix it...

---

Nope, this is not something use mere mortal users can fix.  Only Plusnet can find and stop the accounts that are spewing out so many messages that this limit is hit well before the count resets on the hour.

The fact that they haven't dealt with it despite it persisting on and off for months now implies they just don't care.  Especially as if they did fix this problem it's a safe bet it would help with the other long standing problem of Microsoft not lifting their block on the Plusnet mail servers.

That's the cue for someone like @Townman, @MisterW @plusnettony to say I'm wrong, which I would love to be but my experience strongly suggests I'm not. 

[#8]

I too have been getting 'too many messages in the last hour' errors. I could only send for a few minutes after each hour. I'm hoping that Greenby support have now found the answer.

The outgoing settings I am now using in Thunderbird are:
Server: relay.free-online.net  (if you have a PlusNet email address use relay.plus.net)
SMTP: Port 587
Connection security STARTTLS  - these will ensure that your password is encrypted
Authentication method: Normal password
User name:    [username]@[username].free-online.co.uk (or [username]@[username].plus.net as appropriate), which is the default email address.

My user name was previously set as [username]@free-online.co.uk which worked perfectly for many years with PlusNet, but seems to have been the cause of the problem with Greenby.

For incoming emails I use:

Server: imap.free-online.net
Port; 993
Connection security SSL/TLS
Normal password - again these setting will ensure that your password is encrypted

I hope this helps someone

[#9]

Am I right that the problem seems to be much worse for people with Force9 addresses, sending using relay.force9.net SMTP server?

My mother has a Force9 address that she has used for years and which is too widely known to change, but for some weird internal Plusnet reason her Force 9 internet acccount had to be closed and a new Plusnet account created instead when she upgraded fro ADSL to VDSL/FTTC... which has an email address.

Would this work in Outlook (the app, not the email domain)? Configure emails to be sent using relay.plus.com, authenticating using the PLusnet email address (username) and its corresponding password, but leave the receiving of emails configured to use mail.force9.net and her Force9 address (username) and its password. Does the Plusnet SMTP server check that the From address matches the server and/or username: would it allow logon to relay.plus.net with a Plusnet email address when the From address is a Force9 address?

I'm trying to think laterally for a way thay my mother can send emails, because she is now finding that at almost any time of the hour, sent emails are bouncing with either "too many recipients", or else a "permanent error" (I don't have any further details of that one.

[#10]

I'm no expert and I can only speak from my own experience with my free-online mail account, one of a number legacy ISPs that PlusNet took over and kept on separate email servers. We were told that no changes were necessary on transfer, but it seems that some legacy settings that worked on PlusNet cause problems on Greenby.

I would hope that the settings that seem to be working for me, so far, would also work for other users.

I use Thunderbird, but I assume other email clients, such as Outlook, would use the same Greenby server settings.

For me the key problem seems to be that my Free-online user name was watton@free-online.co.uk but Greenby's user name is the default email address on their system, which is watton@watton.free-online.co.uk.

I don't understand how messages were sometimes getting sent and at other times were rejected, but the wrong username / settings seem to be triggering some sort of spam blocking system on Greenby's servers. Don't ask me how or why.

My best suggestion to others with the problem is to make a note of your existing email server settings (take a screenshot) and then try the ones that worked for me, substituting your own user name. If they don't work for you, then change them back and raise a ticket with Greenby. You can find a list of server settings here https://greenby.com/support/knowledgebase/article/29 Note that some ISPs use .net and some use .co.uk.

If you are not worried about sending an unencrypted password you can use SMTP port 25  and Connection security None

Rising Star: I don't think the 'from' email address used by the email client matters. Sending is governed by the username and settings for the outgoing (SMTP) server, whereas receiving mail uses the incoming (IMAP or POP) server. The simplest way might be to set up TWO email accounts in Outlook for your mother, one for Force9 and one for PlusNet, each with their own settings, so that both can send and receive emails. If thePlusnet email is to be the main account and the Force9 account is now only used for receiving emails, not sending, you could set up a message rule in Outlook to move all messages from the Force9 inbox folder to the PlusNet inbox folder. https://support.microsoft.com/en-us/office/manage-email-messages-by-using-rules-in-outlook-c24f5dea-... 

I hope this helps you

[#11]

My mother is having this problem and it seems to be getting worse, in that outgoing emails are being rejected "too many recipients" even if sent jist after xx:00 when the counter is apparently reset.

She's logged a call with Plusnet. I'm an authorised contact for my mother, so I see the emails which relate to the call. The call history makes an intersting assertion. I want to know whether there is any truth in it. The person who logged the call, seems to have suggested that if she reduces the number of incoming emails on the POP server, this will help outgoing mail to be sent.

Once you have removed the large messages and freed up space, please be aware it can take up to 4 hours for the servers to update so that you can send emails again. (comment by James Anderson of Plusnet)

 I'm intrigued how two weeks of incoming emails (earliest 25 February) can affect the sending of emails from an email client such as Outlook.

There are other issues:

• mail to Hotmail addresses are being permanently blocked by Hotmail because (it seems) Hotmail have blacklisted mail from Plusnet's servers - what are PN doing about resolving this, because an email system that cannot send to some addresses is not fit for purpose.
• incoming mail messages are being displayed twice (always twice, never more than that) on an Android mobile phone which is probably using the Samsung email client. Is there a definitive statement of what the correct POP settings (server, ports, encryption) should be, so I can get the phone's config checked against these. The problem has only recently started happening, whereas the phone config dates back a few years. It does not happen on Outlook on Windows.
  
  I want to check on the plausiblility of the messages-on-server/sending-emails theory before I progress the call further.
  
  Is there a way in PN's Webmail of seeing the total size of all the messages on the server? Looking at the individual sizes, I think the total is about 40 MB which I wouldn't have thought was excessive. 108 messages, dating back to 25 February 2026.

[#12]

Every day now, I'm having to wait to send email on the hour to work around the problem. I'm assuming we're no closer to a fix, because Plusnet are probably not interested, and Greenby... well, they've not exactly impressed during this whole migration fiasco.

[#13]

My impression, from what my mum is reporting to me, is that the problem is getting worse. It used to be that it only affected emails sent in the later part of each hour, but now it's sometimes happening if a failed email is re-set just after the new hour. I suppose it depends a lot on what time (exactly) the counter gets reset.

What is the scope of the problem? Has any one experienced it using a <mailbox>@<username>.plus.com address and relay.plus.net SMTP server, or is it confined to <mailbox>@<username>.force9.co.ok address and relay.force9.net? I've never seen it from my .plus.net address and relay.plus.net, either before migration to Greenby or afterwards. Mum has not been migrated yet.

With reference to my earlier posting about the advice from PN support to delete most of the emails on webmail.plus.net as a way of improving the chances of sending emails, I've done that. It will be interesting to see if it makes any difference whatsoever. I'm sceptical but I'll humour them... 😉

[#14]

@martinund it's affecting everyone, as far as I'm aware. I'm using a plus.com address, and it's definitely worse now than it has been - I'm in the habit of tackling emails just before the hourly reset so I don't have to wait too long to try and resend until it works. This is via webmail, BTW.

[#15]

Thanks everyone for your replies.  Well, I've solved the problem... I've moved domain and email elsewhere.

After best part of 20 years of excellent service from Force9 (and now Plusnet), it's time to move on.  Wasn't that difficult to do either.  My monthly costs have gone up a bit, but that's nothing compared to the hundreds it's just cost me as a result of emails not getting to the recipients who needed to know things in a timely manner.  While I appreciate email is not a guaranteed delivery service from any provider, the fact they did not get through for reasons which appear to be within someone's sphere of influence is irritating.  So, domain moved, email moved, and when broadband contract comes up for renewal... let's see what mood I'm in.