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client incorrect greeting error, how to resolve?

I have a user reporting from time to time getting:
"An error occurred while sending mail. Mail server sent incorrect greeting
4.7.0 geko.sbt.net.au error too many connections from 147.50.1.226"

is this a Thunderbird issue ?

when I search like below, I get nothing, what am I doing wrong?

and, how to fix this, is there anything at this end ? user end ?

# grep 147.50.1.226 /var/log/maillog | wc
407 7142 79129
# grep 147.50.1.226 /var/log/maillog | grep error
# grep 147.50.1.226 /var/log/maillog | grep Error
# grep 147.50.1.226 /var/log/maillog | grep greeting

Comments

Re: client incorrect greeting error, how to resolve?

By Viktor Dukhovni at 12/03/2018 - 21:05

Is that the verbatim message, or just similar? Postfix responds with
a similar message when a client exceeds either the concurrency or the
connection rate limits you have configured:

if (var_smtpd_cconn_limit > 0
&& state->conn_count > var_smtpd_cconn_limit) {
state->error_mask |= MAIL_ERROR_POLICY;
msg_warn("Connection concurrency limit exceeded: %d from %s for service %s",
state->conn_count, state->namaddr, state->service);
smtpd_chat_reply(state, "421 4.7.0 %s Error: too many connections from %s",
var_myhostname, state->addr);
break;
}
if (var_smtpd_crate_limit > 0
&& state->conn_rate > var_smtpd_crate_limit) {
msg_warn("Connection rate limit exceeded: %d from %s for service %s",
state->conn_rate, state->namaddr, state->service);
smtpd_chat_reply(state, "421 4.7.0 %s Error: too many connections from %s",
var_myhostname, state->addr);
break;
}

In both cases Postfix logs a more detailed message to the system
log, so that's where you should have looked for messages relating
to "147.50.1.226".