Cisco Cisco Email Security Appliance X1050 Fehlerbehebungsanleitung
What can cause email delivery delays? How does
ESA message delivery work?
ESA message delivery work?
Document ID: 118548
Contributed by Cisco TAC Engineers.
Oct 10, 2014
Contents
Introduction
Queues
Connections
Network
Logs
Queues
Connections
Network
Logs
Introduction
This document describes a basic overview of how delivery works on the ESA. There are many variables
involved so it is difficult to say what is causing specific messages to be delayed without investigating each
individually.
involved so it is difficult to say what is causing specific messages to be delayed without investigating each
individually.
Queues
The message's recipients are divided up by destination domain queue. The system scans the destination
domain queues on an ongoing basis; the more destinations in memory, the longer each pass of scans will take.
If the system is under heavy load, this can delay the delivery queue scans.
domain queues on an ongoing basis; the more destinations in memory, the longer each pass of scans will take.
If the system is under heavy load, this can delay the delivery queue scans.
Connections
Each delivery connection will send up to 50 messages before closing. If connections are already established,
the system will attempt to send over the open connections. If those connections become full or a particular
connection is taking a long time, the system will try to establish new connections. The number of open
delivery connections is limited by the Destination Controls and Delivery Max Concurrency settings.
the system will attempt to send over the open connections. If those connections become full or a particular
connection is taking a long time, the system will try to establish new connections. The number of open
delivery connections is limited by the Destination Controls and Delivery Max Concurrency settings.
Network
Messages that are larger will take longer to deliver than smaller messages. If the network connection is slow
for any reason, mail delivery will be slowed too. If there are network errors reaching a particular IP for a
destination domain, the messages will be re−queued for another connection. If there are DNS errors looking
up a destination domain or all hosts are unreachable, all mail for that domain will be re−queued until the issue
is resolved. A particular MID may have multiple DCIDs associated with it, with each DCID having to
transmit the full DATA content over the network.
for any reason, mail delivery will be slowed too. If there are network errors reaching a particular IP for a
destination domain, the messages will be re−queued for another connection. If there are DNS errors looking
up a destination domain or all hosts are unreachable, all mail for that domain will be re−queued until the issue
is resolved. A particular MID may have multiple DCIDs associated with it, with each DCID having to
transmit the full DATA content over the network.
Logs
When scanning is complete, the message is "queued for delivery":