Le 22/05/2024 à 12:35, Greg Sims via Postfix-users a écrit :
Thank you again for your feedback on this issue.
I watched the workload in real time this morning and now have more
insight into what is happening. It appears the large ISPs are using
TLS connection as a way to throttle incoming traffic. I looked at the
inbound mail queue and found most of the traffic going to gmail.com.
I believe this is because of the 20 & 25 seconds delays google.com is
injecting into the TLS connection. I can also see no delays for the
smaller ISPs with little traffic. Please see some data below.
Best, Greg
This is a sample of delays= for google.com -- 20 and 25 second delays:
0.01/11/20/0.73,
0.01/9.5/20/0.77,
0.01/0/25/0.74,
0.01/7.6/25/0.91,
0.01/6.9/25/1.1,
0.01/13/20/4.6,
0.01/14/25/0.56,
0.01/14/25/1.1,
0.01/0/0.22/0.72,
0.01/0/0.39/0.79,
Here are delays= from yahoo -- 5.3 second delays:
0.01/0/10/4.1,
0.05/0/5.1/0.95,
0.01/0/5.2/0.68,
0.01/0/5.3/0.57,
0.01/0/0.45/0.42,
0.01/0/5.3/0.42,
0.01/0/5.3/0.34,
0.01/0.39/5.1/0.73,
0.01/0/1.2/2,
0.01/0/5.3/0.34,
And from icloud -- little delay:
0.01/0/0.14/2.5,
0.01/0.02/0.15/2.7,
0.01/0/0.34/11,
0.01/0/0.13/4.9,
0.01/0/0.06/4.1,
0.01/0/0.13/1.5,
Check all your public DNS records/config which concern you outboud
server : PTR, A of your public IP, A and possibly PTR of your EHLO name
if different. SPF/DKIM/DMARC record of the outgoing Mail From
envelope/From header.
Could be caused by bad records or DNS missconfiguration/blackhole or DNS
interoperability issues when distant check your configuration. For the
TCP session establishment check PTR/A/and A of the returned PTR if
different first.
But it could be a client issue too. So a complete hosts tcpdump or
debug_peer_list session for selected test email (use a user defined
specific test transport to enable debug_peer on a specific email
address) would produce more interesting timing trace.
Emmanuel.
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