What does "No Free Threads" in SMTP log mean?

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My SMTP server is refusing all connections with the error “Too busy – no free threads”.

The Service Activity page in the Administration GUI shows a number of stalled SMTP threads. I am using the VSM module.


There have been instances in the past where badly formatted mime messages causing the virus scanner to stop processing attachments. This in turn causes the SMTPthreads to hang waiting for a response from the Virus Scanner.

The first step in resolving this issue is to enable all the logging options for the SMTP service from the Logs > Transaction Levels page in the GUI and then stop and restart the service and The next time the problem occurs, look in the VS log to see what is happening, you should be able to see easily where it stalls. If this does not shed any light on the matter then please forward the logs along with a copy of setup.txt and a copy of the message causing the problem retreived from the gordanotemp directory to support@gordano.com. The support engineers will then scrutinise the message and logs taking appropriate action to rectify the matter.

NOTE: Due to reliability and performance issues, VSM has been replaced by VPP which includes continous signature file upadtes and cleaning options.

Keywords:SMTP threads virus scanner vsm free

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