Hello,
My email server sends lots of emails to networks in China, however they seem to
have packet loss due to what my postfix instance struggles to deliver letters
to them - only few letters occasionally got successfully sent:
$ sudo grep -e abuse@china -e \\.cn /var/log/mail.log | grep -e dsn=2 | awk
'{print$1" "$2}' | uniq -c
74 Sep 10
$ sudo grep -e abuse@china -e \\.cn /var/log/mail.log | grep -e dsn=4 | awk
'{print$1" "$2}' | uniq -c
10243 Sep 10
$
As you can see below, my queue is very large and it is constantly growing:
$ sudo /usr/sbin/postqueue -j | /usr/bin/jq -r '. | select(.queue_name == "deferred") |
.recipients[] | join(": ")' | grep "Connection timed out" |sort | uniq -c | sort
1 [email protected]: connect to sea.net.edu.cn[166.111.204.8]:25:
Connection timed out
1 [email protected]: connect to
oa-mta.21cn.net[182.42.134.193]:25: Connection timed out
1 [email protected]: delivery temporarily suspended: connect to
oa-mta.21cn.net[182.42.129.150]:25: Connection timed out
1 [email protected]: delivery temporarily suspended: connect to
mailc.mailex.Chinaunicom.cn[123.138.59.138]:25: Connection timed out
1 [email protected]: delivery temporarily suspended: connect to
cloudmx.qq.com[121.51.167.59]:25: Connection timed out
1 [email protected]: connect to
oa-mta.21cn.net[182.42.129.150]:25: Connection timed out
1 [email protected]: connect to
oa-mta.21cn.net[182.42.134.193]:25: Connection timed out
1 [email protected]: delivery temporarily suspended: connect to
cloudmx.qq.com[121.51.167.59]:25: Connection timed out
1 [email protected]: connect to cloudmx.qq.com[121.51.167.59]:25:
Connection timed out
2 [email protected]: connect to
oa-mta.21cn.net[182.42.129.150]:25: Connection timed out
2 [email protected]: connect to mx.fj.bnet.cn[183.56.203.132]:25:
Connection timed out
2 [email protected]: delivery temporarily suspended: connect to
oa-mta.21cn.net[182.42.129.150]:25: Connection timed out
2 [email protected]: delivery temporarily suspended: connect to
oa-mta.21cn.net[182.42.134.193]:25: Connection timed out
2 [email protected]: delivery temporarily suspended: connect to
mailc.mailex.chinaunicom.cn[123.138.59.138]:25: Connection timed out
4 [email protected]: connect to mx.chinamobile.com[221.176.66.77]:25:
Connection timed out
4 [email protected]: delivery temporarily suspended: connect to
mailc.mailex.Chinaunicom.cn[123.138.59.138]:25: Connection timed out
6 [email protected]: connect to
mailc.mailex.Chinaunicom.cn[123.138.59.138]:25: Connection timed out
23 [email protected]: delivery temporarily suspended: connect to
mailc.mailex.chinaunicom.cn[123.138.59.138]:25: Connection timed out
61 [email protected]: delivery temporarily suspended:
connect to oa-mta.21cn.net[182.42.129.150]:25: Connection timed out
75 [email protected]: delivery temporarily suspended:
connect to oa-mta.21cn.net[182.42.134.193]:25: Connection timed out
131 [email protected]: delivery temporarily suspended: connect to
mx.chinamobile.com[221.176.66.77]:25: Connection timed out
180 [email protected]: delivery temporarily suspended: connect to
mailc.mailex.Chinaunicom.cn[123.138.59.138]:25: Connection timed out
448 [email protected]: delivery temporarily suspended: connect to
oa-mta.21cn.net[182.42.129.150]:25: Connection timed out
624 [email protected]: delivery temporarily suspended: connect to
oa-mta.21cn.net[182.42.134.193]:25: Connection timed out
However, from my troubleshooting I can see that it is possible to connect to
them:
$ nc -v oa-mta.21cn.net 25
Warning: inverse host lookup failed for 182.42.134.193:
Warning: inverse host lookup failed for 182.42.129.150:
oa-mta.21cn.net [182.42.134.193] 25 (smtp) open
220 chinatelecom.cn
QUIT
$
Can you please suggest me any optimizations for this case? I have already tried
to configure smtp_connection_cache_destinations as well as
smtp_tls_session_cache_database, however it didn't have any observable impact.
Thanks.
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