Recently I erroneusly deleted a message from the dev@api ML, so I tried to 
obtain the message using the ezmlm program facilities 
Unfortunately I noticed that the message index that I can see in the web 
interface of the ML archive is not usable for ezmlm requests because itdoes 
not match with the index used by the ezmlm program.

Christian Lohmaier kindly explained to me the situation :

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> But  (perhaps I'm missing something), does it exist any way to obtain the
> mailinglist-ID  for a given message? or shoud I find it by tries and errors?

One that was delivered to you: Yes, there is a Return-Path header like this:
Return-Path: <dev-return-17945-httpd-your=address@api.openoffice.org>

Where the 17945 would be the mailinglist-ID of that message.

Unfortunately, this header is not added to the web-archive on the ooo site,
and most other web-archives strip many headers as well.

(And getting the mail again, when you still have access to it is
pretty pointless)

So the only way to get it is via the index unfortunately :-(
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I think that this should be fixed, making the "ezmlm-msg-ID" available in the 
web interface of the archive