ok, your SME seems to not have a lot of alteration from the base.
Additional local networks
0.0.0.0/0.0.0.0 via 10.0.0.1 => this is totally insecure.
SHOULD BE REMOVED.
82.80.213.0/255.255.255.0 via 10.0.0.1 => this is insecure as you are allowing relay and local access from the internet to 65534 hosts !
SHOULD BE REMOVED 91.202.169.0/255.255.255.0 via 10.0.0.1 => this is insecure as you are allowing relay and local access from the internet to 65534 hosts !
SHOULD BE REMOVED 10.0.0.0/255.255.0.0 => means you consider as local network : 10.0.0.1 to 10.0.255.254
10.10.100.0/255.255.255.0 via 10.0.0.1 => this is another local LAN , and you consider also as LAN for SME : 10.10.100.1 to 10.10.100.255
10.20.30.0/255.255.255.0 via 10.0.0.1 => this is another local LAN , and you consider also as LAN for SME : 10.20.30.1 to 10.20.30.255
do you really need to have 131068 internet IP to be considered and trusted as local(in other words do you control all of them ) ? why would you do that?
You would say that if you already considered the whole world as local this is not anymore a major consideration !

From now, I would remove those 3 networks. This is a major security concern to have them here.
I would then consider who is having problem connecting to you server to send mail, or having problem to access it in anyway they should. And establish either a vpn or give them a login and password to connect to deliver email.
Your problem delivering email is another issue.
How you server is configured to deliver email ?
- are you handling this locally for your users or have you another remote email server?
- for remote emails do you deliver them directly or are you using your FAI smtp server or another one ?