procmail: getting procmail to exclude hostname while saving Maildir format messages

Question

How do I get procmail to save messages in my Maildir folder, but not include the hostname in the file (message name)? I get the following message names in my new/ sub-folder:

  1464003587.H805375P95754.gator3018.hostgator.com, S=20238_2

I just want to eliminate the hostname. Is that possible to do, using procmail? How? Separately, it is possible to replace the first time stamp with the time-sent time-stamp? Is it possible to prescribe a format for procmail?

Answer 1

No, you can't override Maildir's filename format, not least because it's prescribed to be in a particular way for interoperability reasons. The format is guaranteed to be robust against clashes when multiple agents on multiple hosts concurrently write to the same message store. This can only work correctly if they all play by the same rules. An obvious part of those rules is the one which dictates that the host name where the agent is running must be included in the filename of each new message.

The Wikipedia Maildir article has a good overview of the format's design and history, and of course links to authoritative standards and other primary sources.

If you don't particularly require Maildir compatibility (with the tmp / new / cur subdirectories etc) you can simply create a unique mbox file on each run; if you can guarantee that it is unique, you don't need locking when you write to it.

For example, if you have a tool called uuid which generates a guaranteed unique identifier on each invocation, you can use that as the file name easily;

:0  # or maybe :0r
`uuid`

It should be easy to see how to supply your own tool instead, if you really think you can create your own solution for concurrent delivery. (Maildir solves concurrent and distributed delivery, so the requirements for that are stricter.)

The other formats supported by Procmail have their own hardcoded rules for how file names are generated, though perhaps the simple MH folder format, with a (basically serially incrementing) message number as the file name, would be worth investigating as well. The old mini-FAQ has a brief overview of the supported formats and how to select which one Procmail uses for delivery in each individual recipe.