config/tls: Set min TLS version to 1.0

Better to have TLS 1.0 than no encryption at all.
Default Go client setting of TLS 1.2 is too restrictive
for mail infrastructure with lots of outdated servers.

Author: foxcpp

Diff for: framework/config/tls/server.go

@@ -95,7 +95,7 @@ func readTLSBlock(globals map[string]interface{}, blockNode config.Node) (*TLSCo
 	}, &loader)
 
 	childM.Custom("protocols", false, false, func() (interface{}, error) {
-		return [2]uint16{0, 0}, nil
+		return [2]uint16{tls.VersionTLS10, 0}, nil
 	}, TLSVersionsDirective, &tlsVersions)
 
 	childM.Custom("ciphers", false, false, func() (interface{}, error) {