When I try to setup the Smoothwall to send email alerts via my internal mail server, I find my mail server is rejecting the Smoothwall's attempts to send mails - what can be wrong?
Often mail servers will ask for a full host and domain name from the sending server.
It rarely matters what the actual value is but Smoothwall hostnames do have to include host and domain name. Often we see Smoothwalls only configured with a hostname and no domain. This can cause the receiving to reject the mails.
A full host and domain name can be configured in the Smoothwall administration user interface, under System > Preferences > Hostname.