016-781 means there is no communication to mail.smtp2go.com, which implies a trouble in the DNS.
I see your gateway is just 192.168.1.1, but your DNS is 192.168.1.10, odd , but not impossible.
I would suggest though,disabling Obtain DNS Server address Automatically and then setting the secondary DNS to 18.104.22.168
You will likely need to do a Wireshark trace if it is still giving the same fault. As I stated, it means no connection, if Gateway,DNS,Proxy(If in use) and time are correct it should not happen unless the domain in question is down. It can't be firmware related because it doesn't get to the point of not being compatible
I have a simillar problem. No matter how I set dns,different smtp servers (with and without ssl/tsl), error 016-781 still persist :(
There is no problem with remote printing.