No, it's not a global unique identifier. In fact you cannot even be sure
it will always be there in all mails, depending on your mail processing
chain. Most of the email clients will add one, and most of the mail
transfer agents will also add one if missing, but there's no general
rule of how to create the mail id. Usually it will be unique for the
specific instance of the user/transfer agent which generates it, as it
serves for exact this purpose, to identify the mail instance on the
agent instance, but nothing more.
So: don't use it as a unique identifier.
Cheers,
Csaba.
On Tue, 2004-10-12 at 17:01, Jerry LeVan wrote:
> Hi,
> I am futzing around with Andrew Stuarts "Catchmail" program
> that stores emails into a postgresql database.
>
> I want to avoid inserting the same email more than once...
> (pieces of the email actually get emplaced into several
> tables).
>
> Is the "Message-ID" header field a globally unique identifer?
>
> I eventually want to have a cron job process my inbox and don't
> want successive cron tasks to keep re-entering the same email :)
>
> Jerry
>
>
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