After "November major upgrade" I cannot send mail from any mail client

As described two threads below, yesterday I installed WIN10 "november major upgrade". Since then, I am unable to
send mail from *** any mail client *** on the box. Tried Outlook, Tried LIVE mail, Tried couple of programs
that have "send-mail" feature. Every time i used the same settings for outgoing e-mail server.
These setings work as verified by sending mail when using the same settins from different PC (win XP) on the same LAN.
In Outlook and LIVE mail the error reads as "Error 452.4.1.0 Policy violation . Your host xxx.xxx.xxx.xxxx has no valid reverse DNS. Pleas contact .... blabla". In the apps that have "send mail" feature the error was native "Connection closed gracefully".
I tried to disable Win10 firewall - no avail. I tried to disable my antivirus - no avail. I really need this to be solved :-(

Well, it seems that I am moving forward... I identified the cause. My PC has two Ethernet cards, each connected to different subnet (first 192.168.1.xxx and the second 192.168.192.xxxx). The second subnet is used for my company and internet communication while, the first one is just for reaching the neigbooring company local net. I have fixed IP address on both subnets. In order to avoid internet connection on first subnet, I have set metric 999 on IPV 4 protocol on the corresponding card and neighbooring company forbid my fixed IP address (on the first subnet) in the router. Now the upgrade has, *** god only knows why ***, completely screwed the settings on the first subnet card and has enabled the DHCP feature on the first subnet. So - when I launched the mail client, it used the wrong subnet, thus wrong WAN (that is operated by different ISP), thus it was rejected by the smtp mail server. Question to Microsoft: WHY DID THE UPGRADE CHANGED THE CARD SETTINGS? I disabled the first ethernet card and mail client works. I shall restore the original settings, get rid of doubled listing of the first card in the "active subnets list" (probably caused by me giving the subnet non-default name, and the upgrade assigned the default name to some other piece of data so the same subnet is now listed twice), and all will be as it was before upgrade. I spent 6 hours on this and Microsoft ows me 100 biers.