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Email Security

Can ESA be deployed transparently?

We have an ISP customer that wants to block outbound spam emails coming from their subscribers transparently without any header modification or subscriber's knowing their emails are being analyzed.


The use-case in particular is to block outbound spam generated by compromised systems [botnets] by routing all SMTP traffic to ESA deployed transparently to analyze such email traffic and block them. The ISP wants to safeguard their IPs from being blacklisted because of such outbound spams.


Please note ISP doesn't have control over subscriber's mail servers apart from giving them Internet services only.

Ken Stieers

There's a few headers that will get added (ips/machine names) as the box passes the mail, which you'll probably want to leave for trouble shooting purposes.
You can tell it not to add x-headers for virus scanners and AMP, but I don't see anything for anti-spam... you might be able to use a content filter to delete any headers on the way out.

Thanks Ken. Can you please confirm if ESA be deployed transparently? (In Transparent mode)

Ah... I think I get what you're asking...
NO... you have to configure the email servers that your various clients have to send mail to the ESA. You can't put it in place and not change how mail flows.