Error 421 SMTP Connection limits exceeded when sending mass e-mailing with SmarterMail 16.3.6989
Question asked by paulo.santana - 2/10/2022 at 9:36 AM
Hi friends:

We use SmarterMail Professional Edition, version: 16.3.6989. In the past, SmarterTools support helped us solve a problem where we weren't able to send our newsletter to ~37k e-mails, bu correctly diagnosing we had throttling enabled. Since we disabled it, the newsletter started working its way through all the e-mail list. 

However, at a certain point throughout the process above, we start receiving the error below when trying to send new emails, and the error persists for *hours* after the newsletter is "entirely sent" (actually, most of the list doesn't get sent because of the error, of course). How could we prevent that from happenning? Is this a problem with our SmarterMail setup, as it was with the throttling issue, or is it on our environment? Thanks for any help!

Could not deliver message to the following recipient(s):

Failed Recipient: vendas.microsafe@gmail.com
Reason: Remote host said: 421 SMTP Connection limits exceeded

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Tony Scholz Replied
Employee Post Marked As Answer
Hello Paulo, 

The error you are seeing "421 SMTP Connection limits exceeded" is coming in from the remote server, "Remote host said:" and is not an environmental issues or a setting in SmarterMail but on the server you are connecting to. 

You have reached the number of connections the remote host you are connected to will allow and need to wait for your IP/Host to be released. 

I hope this helps to understand what is happening. 

Thank you
Tony Scholz System/Network Administrator SmarterTools Inc. (877) 357-6278 www.smartertools.com

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