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To ensure that your PureMessage for Microsoft Exchange server is configured to get the best possible spam capture rates:
What is a trusted relay?
An email relay is a type of server used to pass email from one point of the internet to another. Each email contains a list of the email relays it passes through on the Internet. This includes the email server used to send the email - the originating email server.
A trusted relay is a known email server that sends or forward emails to PureMessage. Typical examples of trusted relays include your ISP's SMTP server and any email relays located on your network which are upstream to your PureMessage server(s). These servers can be trusted because they are highly unlikely to be the source of spam email. It is important to understand that servers on the trusted relay list will still relay spam email but are unlikely to be the originating source of the spam.
By default PureMessage will run a reputation check on each email server address specified in an email. When a server is added to the trusted relay list the reputation check for that server is skipped, because the server is "trusted". This has a positive impact on the email scanning speed because a lower volume of reputation checks have to be carried out. It also enables the spam engine to be more deterministic when it matches an email server's address against the known list of spamming email servers. Therefore a higher spam score can be allocated to the email when a match is found.
For more information on how to configure PureMessage refer to the PureMessage user manual.
Another knowledgebase article contains more information on troubleshooting spam blocking on version 3.0 of PureMessage for Microsoft Exchange.
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