AWG Blogs

Sunday, May 15, 2011

DLP "Forwarding agent unavailable" error

If this error is appearing in the /var/log/mail.log of your upstream MTA, when initially setting up a DLP Network Prevent for Email in Forwarding mode, try recycling the new smtp prevent server, before trying anything else.

e.g. errors like (host #.#.#.51[#.#.#.51]
refused to talk to me: 421 4.4.1 Fatal: Forwarding agent unavailable. Closing connection.

Recycling the DLP email prevent server got the following architecture to finally start working:

Outlook --> (port 25) Ubuntu Postfix MTA --> (port 10025) DLP SMTP Prevent --> (port 25) Ubuntu Postfix MTA --> (port 587, TLS) GMail

The upstream MTA's was configured with smtp_use_tls=no, smtp_sasl_auth_enable=no; and with relayhost=(DLP_IP):10025

The DLP server's advanced configuration had RequestProcessor.MTAResubmitPort=25 (changed from default 10026). Next Hop Configuration was set to Forward with Disable MX lookup, and downstream local MTA's IP set in Hostnames.

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