Hello list, Bit of a weird one here. I have hosts at AWS sending mail across a Checkpoint VPN to my main private relay server (it basically serves to relay mail to O365 for in house applications). The problem is that the sending client never receives BYE from server after QUIT. The mail goes through and is delivered ok. This is bad because our timeout is 300s and if you have anything more than a small amount of mail to send, your connections waiting to timeout build up at the client and cause problems with applications. Mail from non-AWS sources does not have this problem across other legs of our Checkpoint VPN.
I have done packet captures at source, destination, and the two Checkpoint FWs which are the VPN endpoints. I can clearly see what appears to be filtering occurring on the QUIT, but I am really struggling to determine where said filtering is coming from. I can recreate issue with a simple mailx command, originally it was reported from a java mail client (so multiple clients exhibit same issue). And before you ask, we have already had AWS support remove the SMTP throttling for this host. We have also looked at Checkpoint logging and can find no evidence it is being throttled at those devices. Source host is Centos 7. Destination host is Centos 6. Both have latest kernel and patches for everything. Postfix version is postfix-2.6.6-8.el6.x86_64. Thanks for any suggestions. Postfix -n below alias_database = hash:/etc/aliases alias_maps = hash:/etc/aliases command_directory = /usr/sbin config_directory = /etc/postfix daemon_directory = /usr/libexec/postfix data_directory = /var/lib/postfix debug_peer_level = 2 html_directory = no inet_interfaces = all inet_protocols = all mail_owner = postfix mailbox_size_limit = 78643200 mailq_path = /usr/bin/mailq.postfix manpage_directory = /usr/share/man message_size_limit = 78643200 mydestination = $myhostname,localhost.$mydomain,localhost,idcsmtp2.$mydomain,idcsmtp5.$mydomain,relay.$mydomain mynetworks = 10.0.0.0/8, 198.112.99.0/24, ***.***.***.***/21 mynetworks_style = class myorigin = $myhostname newaliases_path = /usr/bin/newaliases.postfix notify_classes = bounce, 2bounce, delay, protocol, resource, software queue_directory = /var/spool/postfix readme_directory = /usr/share/doc/postfix-2.6.6/README_FILES relay_domains = $mydestination, $mydomain, example.com, example.com relayhost = [example.protection.outlook.com] sample_directory = /usr/share/doc/postfix-2.6.6/samples sendmail_path = /usr/sbin/sendmail.postfix setgid_group = postdrop unknown_local_recipient_reject_code = 550 source pcap https://insideidc-my.sharepoint.com/:u:/g/personal/fhare_idc_com/ETWH_87w1AhCtSdpgzeoNwYBitZBm4HecmF0WBR2RHKOfA?e=Ln03Cq source Checkpoint VPN endpoint pcap https://insideidc-my.sharepoint.com/:u:/g/personal/fhare_idc_com/ET3RjKJ_3xdOuvog3fPe8xQBUUUK8qQ7VdOSsnA6oiK4yw?e=vADRze destination Checkpoint VPN endpoint pcap https://insideidc-my.sharepoint.com/:u:/g/personal/fhare_idc_com/EdGaYYr_pzBNiKkji2kb034BvBv3LJ6ooMRjXz-2ddp9NA?e=iDaBr0 destination postfix pcap https://insideidc-my.sharepoint.com/:u:/g/personal/fhare_idc_com/EUKXDSXYitxArxc4EeVIELIBVrgufBDnYGIZ3K9BC6GCAQ?e=FnUDNM -- Sent from: http://postfix.1071664.n5.nabble.com/Postfix-Users-f2.html
