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SMTP throttling engine for Sendmail servers

'vthrottle' is an implementation of an SMTP throttling engine for Sendmail. It lets sysadmins control how much email users and hosts may send, hindering the rapid spread of viruses, worms, and spam. Exceptions can be made via a whitelist mechanism, which can be generated manually or with the included tool 'vmeasure'. 'vthrottle' tells the misbehaving client to hold on to the deferred mail and resend it later. 'vthrottle' evaluates mail transactions at the connection, the HELO (or EHLO) statement, and the stated source address of the mail. For each of these, a list is traversed and the observed time interval between observations is evaluated. If the observed interval is shorter than the policy interval, the mail is blocked by sending a failure reply code to the SMTP client; the message is then queued. Because 'vthrottle' uses libmilter, it will not work with other MTAs, only with sendmail.



Verified by

Verified on


Verified by

Janet Casey

Verified on

2 June 2004

Leaders and contributors

Jose Nazario Maintainer

Resources and communication

AudienceResource typeURI
Bug Tracking,Developer,SupportE-mailmailto:jose@monkey.org

Software prerequisites

Required to uselibmilter
Required to usepthreads
Required to usesendmail


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