What are your specific security concerns? Just don't want the camera's connected to the Inet?
I have 3 Argus 2 cameras and they all send emails fine... but I am sending them to a gmail account.
Just as a test... I would set up a temp gmail account and try that to see if it something on your end or with the camera. You say your email server is local... is it in a DMZ... do you manage your own Firewall? Can you see traffic on port 25?
Hope that helps.
Why did I have to contact support, have you gain access (via my password and my camera UID) to my camera put my specific camera into a que of some sort to get upgrade, and it take 2 days to get upgrade? Why are users unable to have the camera check for an upgrade, have it pull down the code and do the upgrade once the code is available? This seems to be an archaic way to perform an upgrade.
You may need to contact Reolink support via email to get them to upgrade your Argus for longer recording times. That is what I had to do and now I can record up to 30 seconds post motion trigger.