I had good luck with GMX mail.
Assuming the smtp port 25 isn't outbound blocked, then the best option to send email is to use your own inbound smtp mail receiver. Use mxtoolbox.com to discover your inbound mx record. These should almost always accept you mail to your own domain.
Example check out gmail.com, use any to send to your gmail account.
gmail-smtp-in.l.google.com 220.127.116.11 60 min Blacklist Check SMTP Test 5 gmail-smtp-in.l.google.com 2607:f8b0:4003:c0b::1a 60 min Blacklist Check 10 alt1.gmail-smtp-in.l.google.com 18.104.22.168 60 min Blacklist Check SMTP Test 10 alt1.gmail-smtp-in.l.google.com 2607:f8b0:4002:c03::1a 60 min Blacklist Check 20 alt2.gmail-smtp-in.l.google.com 22.214.171.124 60 min Blacklist Check SMTP Test 20 alt2.gmail-smtp-in.l.google.com 2607:f8b0:400d:c06::1a 60 min Blacklist Check 30 alt3.gmail-smtp-in.l.google.com 126.96.36.199 60 min Blacklist Check SMTP Test 30 alt3.gmail-smtp-in.l.google.com 2607:f8b0:400c:c11::1b 60 min Blacklist Check 40 alt4.gmail-smtp-in.l.google.com 188.8.131.52 60 min Blacklist Check SMTP Test 40 alt4.gmail-smtp-in.l.google.com 2800:3f0:4003:c00::1b 60 min Blacklist Check
GMX Mail worked. Thanks U1. And thanks Andrew for your detailed response. Even though GMX Mail worked, I like that you provided me with some studying material. I will dig in to it because I like to learn and understand the process.
There are occasions where the inbound SMTP mail receiver might reject the incoming email as spam. IF this should happen, then you want the email sender address to reflect the REVERSE DNS name of the internet connection you are on. To discover this, visit myipaddress.com to find your public IP address. Then using mxtoolbox and do a reverse DNS lookup of your public IP address.
Example: a comcast static IP address of 184.108.40.206 will have a rDNS of
So have the NVR send email using a name like
Of course you first need to determine if the ISP providing services isn't block port 25 SMTP mail. The broadband carriers with dynamic ip's do this often... but rarely on static IPS....
TELNET gmail-smtp-in.l.google.com 25
will respond with
220 mx.google.com ESMTP j14si13351267igh.79 - gsmtp
You should be good to go, an this should work fine for any domain, so long as you are sending to the domain. (This will not relay mail to other domains) and does not require a user name of any sort.... Good Luck..... Andy