File locking of mboxrd-format mbox file

Frank Watt youngoldbloke at
Sun Jun 30 05:23:32 UTC 2019

On 29/06/19 4:22 PM, Ian Zimmerman wrote:
> On 2019-06-29 15:24, Frank Watt wrote:
>> My question is: how do I know what type of file locking that has been
>> in use all these years of using fetchmail?
> AFAIK the default mode for fetchmail is not to touch the mailbox file
> itself at all, but either deliver the message via SMTP to port 25 on
> localhost, or pipe it to a MDA such as procmail.  So your question may
> be a bit confused and you should have asked about _procmail_, not
> fetchmail.

Well, yes, I'm more than a bit confused. I've been using procmail but 
I've been persuaded that dropmail is to be preferred.  Now it makes 
sense that it is not fetchmail  my question is about.

> I happen to know that procmail tries to lock the file in _all_ the ways
> available on the system, for instance on Linux with a dotlock temporary
> file, with flock, and with fcntl.  This is a bit overkill but it means
> procmail is safe to use as long as the other program accessing the
> mailbox uses any locking at all.

So does that mean I don't have to be concerned about lock settings when 
it's only a single user system?

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