关于Exchange Server出现Back Pressure事件15004及错误15005的原因排查问询

Hey there! Let's dig into those Exchange Server errors 15004 and 15005—since you've already ruled out memory and disk space issues via Zabbix, here are the other common culprits to investigate:

• Active Directory connectivity problems
  Exchange depends entirely on AD for configuration data, user auth, and critical system operations. Latency, replication failures, or the server losing connection to domain controllers can trigger back pressure (error 15004) and related 15005 events. Test DC reachability with nltest /dsgetdc:yourdomain.com, and check the Event Viewer under Application and Services Logs > Microsoft > Exchange > Active Directory for related errors.

• Network bottlenecks or latency
  Even if server resource usage looks normal, slow network links between Exchange servers (or between Exchange and other services like transport agents) can delay message processing. Look for packet loss, high latency on network interfaces, or firewalls throttling traffic between Exchange components.

• Faulty or misconfigured transport agents
  Third-party agents (antivirus, anti-spam, archiving tools) can hang or fail to process messages, leading to back pressure. Try temporarily disabling non-Microsoft agents using Get-TransportAgent | Disable-TransportAgent (don't forget to re-enable them after testing) to see if the errors stop.

• DAG replication issues (if applicable)
  If you're running a Database Availability Group, check for replication failures, passive copy errors, or mailbox databases in a failed state. Exchange triggers back pressure if it can't maintain database integrity or replication. Use Get-MailboxDatabaseCopyStatus to verify copy statuses.

• Hidden disk I/O latency
  Zabbix might not capture detailed disk I/O metrics. Even with free space available, high read/write latency (consistently above 0.2 seconds per operation) can slow message processing enough to trigger back pressure. Use Performance Monitor to check PhysicalDisk > Avg. Disk Sec/Read and Avg. Disk Sec/Write counters.

• Misconfigured back pressure thresholds
  Default thresholds in the EdgeTransport.exe.config file (typically in C:\Program Files\Microsoft\Exchange Server\V15\Bin) might have been modified incorrectly. Check the <add key="ResourceMonitoring" ...> section to ensure thresholds match your server's capabilities—always back up the file before editing, and restart the Transport service if changes are made.

• Antivirus scanning conflicts
  If your AV tool scans Exchange-specific directories (transport queues, database files, Bin folder) without proper exclusions, it can lock files or slow operations. Verify your antivirus has the recommended Exchange exclusions to avoid interfering with core processes.

备注：内容来源于stack exchange，提问作者Ilkin Y.