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To specify multiple trusted networks, add multiple "trusted_networks" lines.

I'm an ISP, and mails from our customers, using POP-before-SMTP for authentication, are hitting RCVD_IN_DYNABLOCK.

Just like your MSA has to be told who your POP-before-SMTP users are, SpamAssassin has to be to. There's a custom plugin for just that:

http://wiki.apache.org/spamassassin/POPAuthPlugin

I'm an ISP, and mails from our customers, using authenticated connections from another ISP, are hitting RCVD_IN_DYNABLOCK.

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