![]() Measures against clients that make too many connections (default: 20) the Postfix smtpd(8) server breaks the connection. Seconds or $ smtpd_error_sleep_time, whichever is more. The Postfix smtpd(8) server delays all responses by "error count" When the error count reaches $ smtpd_soft_error_limit, $ smtpd_error_sleep_time (1 second with Postfix 2.0, 5 seconds with (default: 10) the Postfix smtpd(8) server delays all error replies by When the error count is less than $ smtpd_soft_error_limit When the error count reaches $ smtpd_hard_error_limit (default: 10), the Postfix smtpd(8) server delays all non-error andĮrror responses by $ smtpd_error_sleep_time seconds (default: 1 When the error count reaches $ smtpd_soft_error_limit SMTP clients must wait until an smtpd(8) server process becomes available. Increase until it reaches the smtpd(8) server process limit, and new When too muchĭelay is configured, the number of simultaneous SMTP sessions will IMPORTANT: These delays slow down Postfix, too. The behavior is Postfix version dependent. The idea is to slow down a run-away client in order to limit resource Unimplemented, when a client request violates access restrictions, or whenĪs the per-session error count increases, the smtpd(8) serverĬhanges behavior and begins to insert delays into the responses. The error count is reset when a message is transferred successfully,Īnd is incremented when a client request is unrecognized or The Postfix smtpd(8) server maintains a per-session error count. Slowing down SMTP clients that make many errors Section describes how Postfix deals with clients that make a large SMTP clients with the same number SMTP server processes. With the above setting, Postfix 2.0 and earlier can serve more You can speed up the handling of smtpd(8) server error replies This means that all clients experience poor performance. New clients must wait until a server process becomes available. When your Postfix smtpd(8) server process limit is reached, So that more smtpd(8) server processes are needed to handle the When the smtpd(8) server replies slowly, sessions take more time, However, these delays also slow down Postfix. Pauses before reporting an error to an SMTP client. With Postfix versions 2.0 and earlier, the smtpd(8) server See the STRESS_README and POSTSCREEN_READMEĭocuments for measures that help to prevent SMTP server overload. Limit as specified in master.cf, new SMTP clients must wait untilĪ process becomes available. If the number of smtpd(8) processes has reached the process If Postfix logs the SMTP client as "unknown" then you haveĪ name service problem: the name server is bad, or the nfįile contains bad information, or some packet filter is blocking Operation as described in the DEBUG_README document and see Turn off your header_checks and body_checks patterns and Of trouble as described in the DEBUG_README document, and When Postfix responds slowly to SMTP clients: This eliminates lookups for addresses in remote domains,Īnd eliminates lookups of partial addresses. Server to a shared forwarding server to reduce the number of lookupsĮliminate unnecessary LDAP lookups, by specifying a domainįilter. If you run multiple Postfix systems, point each local name Run a local name server to reduce slow-down due to DNS Read and understand the maildrop queue, incoming queue,Īnd active queue discussions in the QSHAPE_README document. qmqp-sink, QMQP message dump General mail receiving performance.They are normally not installed with Postfix. The following tools can be used to measure mail system performance Tuning the number of processes on the system.Tuning the number of recipients per delivery.Tuning the number of simultaneous deliveries.Tuning the frequency of deferred mail delivery attempts.Measures against clients that make too many connections.Slowing down SMTP clients that make many errors.Doing more work with your SMTP server processes.General mail receiving performance tips.High volume environments should avoid RBL lookups, Starvation, and if any latency creeps in, content filter throughput Your contentįilter will run with a small concurrency to avoid CPU/memory As much as possible avoid performing queries against externalĭata sources with a high or highly variable delay. Then make sure to avoid latency in the content filterĬode. Respective information in the FILTER_README and SMTPD_PROXY_READMEĭocuments. Those problems first, using the DEBUG_README document as guidance.įor tuning external content filter performance, first read the System is unable to receive or deliver mail, then you need to solve Performance of Postfix systems that already work. The hints and tips in this document help you improve the
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