I think spamdyke implements greylisting by sending a 421 Temporary Failure code on first connection. That might be what's happening here.
Greylisting is off by default, but if you have it turned on you could set `graylist-level` to `none` to turn it off. If you want to keep it on but just fix it for that specific domain, you should be able to configure exceptions by adding appropriate `graylist-exception-ip-entry` or `graylist-exception-rdns-entry` entries. Incidentally, I tend to favor disabling greylisting these days. The original intention was to protect against spam clients that couldn't recognize the 421 error as indicating a temporary condition: they'd try once, get an error code, and go away. But from what I see in my own server logs, many -- most? -- spam clients these days just keep attempting redeliveries until either something gets delivered or they hit some threshold number of retries. Greylisting is no help against those. Angus Alessio Cecchi via spamdyke-users wrote on 3/3/21 12:22 PM: > Hi, > > when a specific company send an email to us we receive the messages many > times, but only if they insert into recipients about 50 email address of > the same domain, if they sent the same email to only one recipients all > works fine. > > After some investigation, with "full-log-dir" enabled, we discovered > that our qmail send a "421 timeout" to remote server but when the email > is already accepted, so the remote server try again and so on. > > Debug log, please note the delay from the last . and the error, five > minutes and note that "421 timeout" error was sent before of "250 ok" > from qmail: > > ======== > > [...] > 03/02/2021 12:03:00 FROM REMOTE TO CHILD: 3 bytes TLS > . > > 03/02/2021 12:08:01 LOG OUTPUT TLS > ERROR(tls_write()@tls.c:678): unable to write to SSL/TLS stream: The > operation failed due to an I/O error, Connection reset by peer > ERROR(output_writeln()@log.c:104): unable to write 37 bytes to file > descriptor 1: Connection reset by peer > > 03/02/2021 12:08:01 FROM SPAMDYKE TO REMOTE: 37 bytes TLS > 421 Timeout. Talk faster next time. > > 03/02/2021 12:08:01 LOG OUTPUT TLS > TIMEOUT from: u...@company.biz to: u...@partnercompany.biz origin_ip: > 40.107.3.43 origin_rdns: > mail-eopbgr30043.outbound.protection.outlook.com auth: (unknown) > encryption: TLS reason: TIMEOUT > > 03/02/2021 12:10:06 FROM CHILD, FILTERED: 28 bytes TLS > 250 ok 1614683406 qp 12548 > > 03/02/2021 12:10:06 - TLS ended and closed > > 03/02/2021 12:10:06 CLOSED > > ======== > > So I set the timeout from 600 to 1200 in qmail-smtpd, remove > "idle-timeout" from spamdyke, and disable the softlimit, the error > change but the problem is still present: > > ======== > > > 03/02/2021 13:59:27 FROM REMOTE TO CHILD: 3 bytes TLS > . > > 03/02/2021 14:06:34 LOG OUTPUT TLS > ERROR(tls_write()@tls.c:678): unable to write to SSL/TLS stream: The > operation failed due to an I/O error, Connection reset by peer > ERROR(output_writeln()@log.c:104): unable to write 26 bytes to file > descriptor 1: Connection reset by peer > > 03/02/2021 14:06:34 FROM CHILD TO REMOTE: 26 bytes TLS > 250 ok 1614690394 qp 765 > > 03/02/2021 14:06:34 LOG OUTPUT TLS > ALLOWED from: u...@company.biz to: u...@partnercompany.biz origin_ip: > 40.107.0.68 origin_rdns: mail-eopbgr00068.outbound.protect > ion.outlook.com auth: (unknown) encryption: TLS reason: > 250_ok_1614690394_qp_765 > [...] > ALLOWED from: us...@company.biz to: us...@partnercompany.biz origin_ip: > 40.107.0.68 origin_rdns: > mail-eopbgr00068.outbound.protection.outlook.com auth: (unknown) > encryption: TLS reason: 250_ok_1614690394_qp_765 > ERROR(tls_read()@tls.c:620): unable to read from SSL/TLS stream: The > operation failed due to an I/O error, Unexpected EOF found > > 03/02/2021 14:06:34 - TLS ended and closed > > 03/02/2021 14:06:34 CLOSED > > ======== > > Any suggestions? > > Thanks > > -- > Alessio Cecchi > Postmaster @ http://www.qboxmail.it > https://www.linkedin.com/in/alessice > > > > _______________________________________________ > spamdyke-users mailing list > spamdyke-users@spamdyke.org > https://spamdyke.org/mailman/listinfo/spamdyke-users > _______________________________________________ spamdyke-users mailing list spamdyke-users@spamdyke.org https://spamdyke.org/mailman/listinfo/spamdyke-users
