Messaging Gateway (SMG) defaults to 2,000 as the maximum number of simultaneous SMTP connections. The SMG Control Center (CC) web interface allows this limit to be configured via the Administration > hosts > Configuration > SMTP > Advanced Settings page.
The Advanced Settings page does not limit the value that can be entered into the Maximum Number of Connections field but will generate an error message if the limit is set higher than 1000000.
Error text: The 'Maximum number of connections' must be an integer between 1 and 1,000,000.
The "Maximum number of connections" field does not impose a limit on the number of digits it will accept and does not otherwise warn when the value is set too high.
The maximum number of simultaneous inbound connections that can be set is 1,000,000.