Question regarding FLOCK or POSIX with Sendmail 8.13.x and MailScanner.

Duncan, Brian M. brian.duncan at
Wed Nov 1 23:33:29 GMT 2006

> Posix is a "safer" method of locking, so you shouldn't have
> problems switching. There are risks of NOT switching to
> posix. There have been symptoms as benign as mail delivered
> more than once, to unmatched qf/df files being left behind.
> You have been lucky what you have not had any problem with
> flock, and you should not depend on MailScanner detecting the
> proper setting.  In the current versions of MailScanner.conf
> you have the following comment;

OK Thanks, I am not familiar with different types of locking files under

> # How to lock spool files.
> # Don't set this unless you *know* you need to.
> # For sendmail, it defaults to "posix".
> # For sendmail 8.12 and older, you will probably need to
> change it to flock, # particularly on Linux systems.
> # For Exim, it defaults to "posix".
> # No other type is implemented.
> Lock Type =
> It does not mention any type of auto detection, I believe
> because Julian had too many problems with its function.
> Change it to posix with sendmail 8.13.
> MailScanner --lint will tell you what is currently running.

I figured it was "auto detect" based on the For sendmail, it defaults to
posix comment above. (Mine are using Sendmail, and it's blank it is
defaulting to flock)

I will be setting them all to Posix then specifically.


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