If you, or somebody trying to send an email to you, gets an error message that the "Address does not pass the Sender Policy Framework", it means that the senders email address does not match the domain of the senders official outgoing mail server.
When an email provider employs
SPF, it has the effect of ensuring that provider's clients use the official mail servers belonging to that provider.
The use of
SPF ensures that an email coming from a particular user has arrived via an official mail server for the domain name they are using. This prevents spammers from using any old email address and sending their junk mail to anyone else via any mail server.
It means that (without access to your password) spammers can no longer forge your email address and relay email to another email provider that also uses
Note: This is why it is imperative that you NEVER respond to emails appearing to have come from Spiderweb, that request your log in details or other personal information. Spiderweb will never request this information by email.
To be able to send an email using an @spiderweb.com.au email address you must also use the Spiderweb mail server as the outgoing mail server and also tick the box that says "my outgoing server requires authentication". This identifies you as a Spiderweb user before allowing you to use a Spiderweb address to send mail.
If you receive an error message about an SPF problem when trying to send an email to an email address hosted on the Spiderweb mail server, then there is a good chance that you are not using the correct outgoing mail server setting for the @domain part of your email address.
Although you may be able to send to anyone else other than Spiderweb hosted addresses, that only means those addresses are hosted by mail servers that do not yet employ SPF checking. More details about Sender Policy Framework can be found at Wikipedia and OpenSPF.