Here the Screenshot from the SMTP-settings:

I use for WPPizza a separate receive-connector with port 2525 in Exchange 2010, which is designed only accepting authorized senders for relaying mails to any receivers.

Here the SMTP-Log when testing:

2017-11-14T00:46:01.991Z,PC09\RoutingInbound,08D51ED31B06BCC6,0,192.168.0.9:25,192.168.0.9:57931,+,,
2017-11-14T00:46:01.991Z,PC09\RoutingInbound,08D51ED31B06BCC6,1,192.168.0.9:25,192.168.0.9:57931,*,SMTPSubmit SMTPAcceptAnySender SMTPAcceptAuthoritativeDomainSender AcceptRoutingHeaders,Set Session Permissions
2017-11-14T00:46:01.992Z,PC09\RoutingInbound,08D51ED31B06BCC6,2,192.168.0.9:25,192.168.0.9:57931,>,220 SMTP ready,
2017-11-14T00:46:01.992Z,PC09\RoutingInbound,08D51ED31B06BCC6,3,192.168.0.9:25,192.168.0.9:57931,<,HELO PC09.***.at,
2017-11-14T00:46:01.992Z,PC09\RoutingInbound,08D51ED31B06BCC6,4,192.168.0.9:25,192.168.0.9:57931,>,250 pc09.***.at Hello [192.168.0.9],
2017-11-14T00:46:01.992Z,PC09\RoutingInbound,08D51ED31B06BCC6,5,192.168.0.9:25,192.168.0.9:57931,<,MAIL FROM:<wordpress@pizzeria-***********.at>,
2017-11-14T00:46:01.992Z,PC09\RoutingInbound,08D51ED31B06BCC6,6,192.168.0.9:25,192.168.0.9:57931,*,08D51ED31B06BCC6;2017-11-14T00:46:01.991Z;1,receiving message
2017-11-14T00:46:01.992Z,PC09\RoutingInbound,08D51ED31B06BCC6,7,192.168.0.9:25,192.168.0.9:57931,>,250 2.1.0 Sender OK,
2017-11-14T00:46:01.992Z,PC09\RoutingInbound,08D51ED31B06BCC6,8,192.168.0.9:25,192.168.0.9:57931,<,RCPT TO:<*******@gmx.net>,
2017-11-14T00:46:01.992Z,PC09\RoutingInbound,08D51ED31B06BCC6,9,192.168.0.9:25,192.168.0.9:57931,*,Tarpit for '0.00:00:20',
2017-11-14T00:46:21.995Z,PC09\RoutingInbound,08D51ED31B06BCC6,10,192.168.0.9:25,192.168.0.9:57931,>,550 5.7.1 Unable to relay,
2017-11-14T00:46:21.995Z,PC09\RoutingInbound,08D51ED31B06BCC6,11,192.168.0.9:25,192.168.0.9:57931,<,QUIT,

You see, mail was sent via Port25 as anonymous user and not authorized via Port2525.

All entries for SMTP, you see in the above screenshot, are ignored. Only basic settings for php-mail take effect.
In the previous version (V2), these SMTP-settings are working very well.
Manually entering the values as defaults in the php-mail-programs solves the problem for me.

Regards