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421 Too many concurrent SMTP connections; please try again later.

Last Modified: 2013-12-17
We have to sent one news letter every day and we have 13000+ emails on the list. Our PHP script using socket and its work fine on the server from last one month.

But we are facing the problem from Tuesday 7th June 2011. while sending the mails we got following error message after sending initial 64 mails and then after some mails are sent fine and some stuck due to following error.

"421 Too many concurrent SMTP connections; please try again later. "

we are using one and one dedicated linux server, I have contacted 1and1 team but still the did not come with any solution why this problem is there as this script running fine from 1 month.

Please suggest some solution ASAP as we are struggling to sent the mails every day.

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