Hello, Thomas Walter via mailop wrote on 07.06.21 at 21:08:
And there's also systems that send a 5xx and immediately disconnect without waiting for the "quit" from the initiating party to properly terminate the SMTP session. In those cases MTAs following the RFCs see this as a failed connection and try again, no matter if the return code specified a permanent or temporary issue. It's been a while since I tracked systems like that, but it happened.
t-online.de mail servers do that when they block IPs. Actually helpful, because it allows getting things sorted out before the mail gets bounced back as undeliverable.
Florian _______________________________________________ mailop mailing list mailop@mailop.org https://list.mailop.org/listinfo/mailop
