SMTP setup on Window 2012R2

A) In IIS manager, SMTP Virtual Server > Properties > Delievery > Outbound Connections. The option for Limit number of connections must NOT BE 0.Unchecked the 0 option and restart the SMTP server.
OR maybe just hung. So
B) Restart the 'Simple Mail Transfer Protocol (SMTP)' service
OR
C) just make IISRESET and fixed

Make the above and if not fixed ti may be DNS problem or something more sophisticate. If problem exist I will send you more details

Enable logging on SMTP to determine what is going on.
SMTP is under the iis iis management console 6.0
Set detailed logs and check what happens when it tries to send.

Walk me through your setup a little more.  Is a device on your network trying to relay email off your 2012 server?  Are you sending email directly to the internet from your server or are you using a smarthost?  I've used this guide in the past successfully, ensure you follow each step carefully:

http://www.vsysad.com/2014/09/setup-and-configure-smtp-server-on-windows-server-2012/

The messages get queued up suggesting an issue when trying to send. Log access is a way to get a clearer picture.

@arnold - yes I agree that's why I asked about the smarthost

I understand, the log is an all encompassing spurce of info that could answer all questions and help the asker resolve the issue.

Thx... only this messages is logged

#Date: 2020-01-02 03:19:43
#Fields: time c-ip cs-method cs-uri-stem sc-status
03:19:43 192.168.2.5 EHLO - 250
03:19:43 192.168.2.5 MAIL - 250
03:19:43 192.168.2.5 RCPT - 250
03:19:43 192.168.2.5 DATA - 250

Beside Window smtp server, is there any free smtp service that I can try ?

Thx again..

Under the log you can increase the info that is recorded, based on the message status 250 all things went through.

Seem that I can't receive the email, even go to email or my company account.....

Also check the spam folder and no email there... Thx

Increase the detail recorded in the log.
prior comments listed the various things to look for.
From the log entry you posted, it only reflects an email your server accepted.

Increase the log detail but can't find any hints....

#Software: Microsoft Internet Information Services 8.5
#Version: 1.0
#Date: 2020-01-02 09:11:08
#Fields: c-ip cs-username s-sitename s-computername s-ip s-port cs-method cs-uri-stem cs-uri-query sc-status sc-win32-status sc-bytes cs-bytes time-taken cs-version cs-host cs(User-Agent) cs(Cookie) cs(Referer)
192.168.2.5 XXX-Monitor SMTPSVC1 XXX-MONITOR 192.168.2.5 0 EHLO - +XXX-Monitor 250 0 207 16 0 SMTP - - - -
192.168.2.5 XXX-Monitor SMTPSVC1 XXX-MONITOR 192.168.2.5 0 MAIL - +FROM:<simon@abc.com> 250 0 38 25 0 SMTP - - - -
192.168.2.5 XXX-Monitor SMTPSVC1 XXX-MONITOR 192.168.2.5 0 RCPT - +TO:<john@gmail.com> 250 0 31 28 0 SMTP - - - -
192.168.2.5 XXX-Monitor SMTPSVC1 XXX-MONITOR 192.168.2.5 0 DATA - <XXX-MONITORC8wSA1Xv00000003@XXX-Monitor.abc.com> 250 0 144 219 0 SMTP - - - -