[TriLUG] Email header message IDs

[Aaron Schrab]

At 21:37 -0400 12 Mar 2013, Kristopher Kane <kristopher.kane at gmail.com> wrote:
>How *unique* are those? Perhaps a better question: Should I worry about
>collisions if I were to use it as a row ID?

According to the standards, it should be safe to treat them as unique.  
In practice that seems to be fairly close to true, but there are 
occasional exceptions.  Soon after I started running a mailing list 
server back in 1996, I came across one sender using some Microsoft mail 
client which would use the same Message-ID for every message that it 
sent which caused the list software that I was using to filter those 
messages out as duplicates.

The following URL seems to indicate that Outlook still has some issues 
in that area.

http://serverfault.com/questions/390199/two-emails-receiving-the-same-message-id