Is the 421 error appearing in a non-delivery report (NDR, a.k.a. "bounce message") that senders receive some hours after sending you an email?
If so, the 421 message should have some additional details in it, including maybe a 4-part numeric code, e.g. 220.127.116.11. Knowing what that is might help diagnosis.
Presumably your BT Internet mailbox isn't stuffed full of messages?
Also, if you have your own domain registered somewhere and are using email forwarding from that domain into your btinternet.com mailbox then perhaps you've got the same problem as I have. See https://community.bt.com/t5/Email/421-Too-many-messages-1-5-6-3-from-nn-nn-nn-nn-when-forwarding/td-...
If you search this forum you'll find multiple reports of this issue - and disappointingly consistent reports of BT simply not listening, understanding or trying to fix the problem with THEIR SMTP servers.
I have just hit this problem where a domain I own has a distribution list that includes people with a BT address. Sending to this results in a NDN stating:
----- Transcript of session follows -----
... while talking to mx.bt.lon5.cpcloud.co.uk.:
>>> MAIL From:<firstname.lastname@example.org> SIZE=10085
<<< 421 Too many messages (18.104.22.168) from 22.214.171.124
<list of people the BT email address>
Deferred: 421 Too many messages (126.96.36.199) from 188.8.131.52
I contacted support for where my Email dist list is held (184.108.40.206) is their server - they "helpfully" responded that this is a known issue - they have been unable to get to BT to do anything about and that I should contact BT. I told this I didn't think this was an acceptable response and reading here it appears plenty of other people have had this issue (in various forms) when trying to send TO a BT email address and BT simply do nothing.
In this day and age that type of support is shocking. I will continue to try and escalate my issue, but I don't have a good feeling about it BT listening or doing anything about it.
BT didnt want to know as it was outlook i was using and not there webmail but it seems to have sorted itself out (or BT have done something there end) as its been working for the last couple of days .So fingers crossed it stays like that??
I have the same problem. Has anyone found an answer? This has been going on for five years or more!! The server responded: 421 Too many messages (220.127.116.11) from 18.104.22.168'
I found a very helpful post here:
The critical part is " I then contacted BT again, via the "I'm thinking of leaving BT" option. The result was (a) another year's broadband and phone service with a big discount and a Home Hub 5 free of charge; and (b) access to BT Tech Experts (normally chargeable, also free of charge) who eventually discovered the messages counter and reset it. There was no explanation as to why is was set at a value which stopped me send messages, but I'm pleased to be able to send messages again "
So do not let BT tech people bamboozle you with "it's an Outlook problem". I eventually got through to someone who admitted it was a BT problem. He could sort out my current non sending, but couldn't say it wouldn't happen again.
I believe I know what triggered my problem. I send out messages to a group of people using a program called send personally, so each recipient receives a personalised message. This results in a number of emails being sent in quick succession. By searching on the web I found that BT set a limit of how many messages can be sent within a minute (it's not clear, but may be 30 messages per minute). The big problem is that once this happens, you are blocked from sending any more emails.
I shall be pursuing this further with BT, without any great hopes of a successful outcome.
This just happened to my wife's email address. "421 - too many messages from xx.xx.xx.xx"
I complained to BT and after half an hour on the chat line they agreed to organise a call from a technician.
No acknowledgement from BT that anything was wrong. Standard "We do not support Outlook" response.
After two days unable to send email - suddenly everything's OK again.#
This technician obviously found the counter and reset it! But he would not admit it. Kept asking if he could now close the issue.
I had this problem: BT server refused to accept sent messages, returned "421 too many messages" error.
It came OK after a day (24hrs), then I could once again send messages as normal. So my first advise would be to wait.
Clearly from the forum posts, others have had more trouble with this, having to go to BT Support. But at least one got a solution without having to pick up the phone.
FYI, I think I triggered this by sending a large - 16M - message. Certainly I did not send a lot of messages.
I have suffered exactly the same problem and scripted response from the help line. Complete denial of any problem on their server and "we can only help you with web mail" ... "we cannot help you with the settings on Outlook" .."the problem has to be with your settings" ... "there is nothing wrong with our system"" Complete **bleep**! This has to be one of the most unhelpful help lines I have ever encountered. I am seriously looking to leave BT altogether as a disgruntled customer.