How to Check Sendmail Queue
Check whether Sendmail mail is piling up and retry queued messages manually.
Before you start
Step-by-step instructions
1. Check current mail queue
Run mailq to see whether mail is currently queued on the server.
mailqIf many messages are listed, mail may be stuck or delayed in the queue.
2. Check the queue directory directly
If needed, inspect the actual queue directory contents.
ls -al /var/spool/mqueueThis lets you confirm directly whether queue files are accumulating inside the Sendmail spool directory.
3. Retry queued mail manually
If messages are waiting in the queue, force Sendmail to retry delivery manually.
sendmail -q -vIt tells Sendmail to process the queue immediately and shows detailed output while delivery is retried.
Common issues
This may mean the remote mail server is rejecting or delaying delivery, or local DNS or routing is failing.
Check mail logs to confirm whether authentication, DNS, relay, or remote rejection errors are occurring.
If there are no queued files, the delivery issue may not be caused by queue buildup at all.
About this guide
This guide shows how to check whether mail is piling up in the Sendmail queue and how to force queued messages to be retried manually.
How to follow this guide
- Use mailq to check whether mail queue is building up.
- Check the mqueue directory directly if needed.
- Run sendmail queue processing manually to retry delivery.
Why use this method?
If mail is not leaving the server properly, checking the queue is one of the fastest ways to confirm whether delivery is delayed or stuck.
Frequently Asked Questions
What does mailq show?
It shows the current Sendmail mail queue and whether messages are waiting to be delivered.
What is /var/spool/mqueue?
It is the directory where queued Sendmail messages are stored temporarily.
What does sendmail -q -v do?
It forces Sendmail to process the queue immediately and shows verbose output.
Does a large queue always mean Sendmail is broken?
No. It can also mean the remote mail server is unavailable or delayed.