Google filtering email, blocking server


Well-Known Member
Jan 2, 2004
Fighting this problem for two days now...

I have three particular domains that have ANY type of mailing list. Two use the cpanel mailing list functionality, the third uses software on their local PC to send mass mail one message at a time.

Problem: starting yesterday, emails are piling up on the server. The common thread is that messages to any recipient who in some way has their email filtered by google are stuck on the server with the following message:

Connecting to []:25 from ... connected
SMTP<< 421-4.7.0 [] Our system has detected an unusual amount of
421-4.7.0 unsolicited mail originating from your IP address. To protect our
421-4.7.0 users from spam, mail sent from your IP address has been temporarily
421-4.7.0 blocked. Please visit
421 4.7.0 to review our Bulk Email Senders Guidelines. m4si15094359qae.63 - gsmtp
Problem is, I'm not showing any unusual traffic. ALL email is routed through that IP, although I have the range 146-150 available. I've checked each IP and none are blacklisted. Over the past couple of days, the third client noted above sent out two mass mails that totaled about 1500 messages. Last night, messages in the queue cleared out, but the number has been climbing again today after I instructed these three clients to NOT send any mass mails while I try and find out what's going on.

This afternoon I tried to use another of my IP addresses, one that I've NEVER used for anything, and I get the same message, albeit with the new IP address.

The link to google is a joke and contains ZERO helpful information. @#^#$^ Google!!

Domains that are producing this problem are, for example:,, There are others of course, and they all give the same message.

I'm at wits end as to how to fix this. I fail to see how an IP that I've never used, that does NOT show up on any blacklists, can somehow instantly have "an unusual amount of unsolicited mail".


Staff member
Apr 11, 2011
Hello :)

It's difficult to know the exact reason why the emails are temporarily blocked by the remote mail servers because there are unpublished rules in place by those servers. Google does provide the following URL with additional information:

You may want to try contacting their support if you feel they are incorrectly blocking email from your server.

Thank you.