[exim] "Introduce a delay into the SMTP transaction" - conne…

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Author: SW & Work SaS
Date:  
To: exim-users
Subject: [exim] "Introduce a delay into the SMTP transaction" - connection timeout
Hi all,

I'm having a problem sending email to a particular network.
We have Exim 4.87 and is working quite well without particular problem.

Lately one of the users noted that he has problem sending to 4 particular
domains.
I checked it and it appears that all are giving connection timeout.
All are hosted on a particular network.

Doing an email verification with verify-email.org give back an ok, the
destination email is correct.

But doing a check with dnsstuff give out a failure with the mail server
connection
answer: xxx.xxx.xxx.xxx | failed message send with: messaging failure: Time
out occurred or Remote server closed connection prematurely

and doing a check with mxtoolbox give a warning for the SMTP transaction
time
SMTP Transaction Time     15.297 seconds - Not good! on Transaction Time


I can telnet the mail server and they have exim 4.89
the answer time to telnet is about 19 seconds

I'm rather sure that they have cPanel in place with the new tarpitting
choice on
Introduce a delay into the SMTP transaction for unknown hosts and messages
detected as spam

But, unfortunately, we have no connection with this network and a first
request to them has been refused as we have no active services with them.

I tried to put these set in the smtp transport of our exim conf
connect_timeout = 10m
command_timeout = 5m
data_timeout = 5m
final_timeout = 10m
but they did not help.

Question, is there anything I can do (or try) to manage the long initial
delay while connecting to this servers ?
There should be something as verify-email.org manage to go on and do the
recipient check.

Thanks in advance for any help you can offer.

Best Regards
Flaviano