That's interesting, I wonder why they decided adding random letters? It reminds me that I used to get a bunch of spam to completely bogus addresses for example:

     E1iusbp-00017V-NM@steve.org.uk

It took me a while, but I realized that these were Message-ID headers that were being used as email-addresses, I just assumed there were some badly written scrapers out there, treating "blah@blah" as an email address and harvesting all such matches.