Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I am running a Postfix server and I would like to know the meaning of suffixes that mail filenames have. For instance:,S,S

And also, what's the criteria to assign them? I've been searching information on this topic, but I have only found references to procmail mechanisms.

share|improve this question
up vote 3 down vote accepted

The 2 indicates that each character following the comma is a flag.

The S flag means "seen" (i.e. the message has been read).

share|improve this answer
To clarify: this is NOT a procmail (or even Postfix) specific thing: It is part of the maildir inbox format, and is supported by a number of MTAs and MDAs (and even used by a few MUAs apparently) – voretaq7 Oct 5 '12 at 21:17
I know that (hence the link to the Maildir spec). The OP didn't. – Kevin DeGraaf Oct 5 '12 at 21:21
I know you know that Kevin (because you linked to the spec), I also know the OP didn't (because they asked the question) and don't want them wandering around with a mistaken impression should the link to the spec not be a good enough hint :) – voretaq7 Oct 5 '12 at 21:25
Fair enough. In the future, I'll explain to OPs: "This isn't a foo issue, it's a bar issue, and here's the answer and the bar specification." :-) – Kevin DeGraaf Oct 5 '12 at 21:31
Thanks for this clarifying discussion ^_^ IMHO the first comment should've been made to my post, not the answer. – elitalon Oct 6 '12 at 16:01

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.