The From Address is an email address and is required. If a Server Address is specified, put your client email address in the From Address, as the server may require this.

Use the Server Address, Server Port, Username and Password to direct outbound email messages through a mail server.

The Server Port defaults to 25, but port 587 may be required when you specify a Server Address.

The Overriding Domain is used to forge the sender Domain Name in the outgoing Email message. This might be necessary, for example, if this device is located behind a firewall whose IP Address resolves to a different Domain Name than this device. For SPAM protection, many SMTP servers perform reverse lookups on the sender IP Address to ensure the Email message is really from who it says it's from.