[e2e] Internet email performance study

Robert Beverly rbeverly at rbeverly.net
Wed Apr 20 11:26:40 PDT 2005

Hi all,

We're looking for operational-types lurking on the list with experience 
running large mail servers.  In particular, we have collected a large 
amount of data as part of an Internet email performance study that we 
cannot entirely explain. If you can help us or are simply curious about our 
findings, we'd love to hear from you.

WHAT WE DID: Briefly, we used SMTP bounce-backs as the basis of an email 
active measurement survey.  Using random addresses as unique identifiers, 
we measure latency, loss, paths, etc. to a large set of Internet 
MTAs.   Approximately 1/3 of all servers we've surveyed respond with 
bounce-backs.  We've found some interesting results.  For example latencies 
of days (30 days in once instance).

WHAT WE DON'T UNDERSTAND:  Most servers behave as we expect, either always 
replying with bounce-backs or never replying.  However, some exhibit odd 
and seemingly non-deterministic behavior.  For example, a server will 
respond to all emails for weeks, and then reply to only a fraction (e.g., 
25-75%) of the emails in a seemingly random pattern for some period of time 
(e.g, 4 hours).  Further, we often see these patterns correlated within a 
domain (e.g., a subset of the MTAs will enter and exist this loss mode at 
the same time).  We are fairly certain that the loss is an artifact of the 
MTA behavior or local administration.  While we can guess reasons this 
might occur, we have yet to find an administrator who can explain this 
behavior with an architecture used in practice.

More details on the project including our exact methodology, plausible 
explanations for the loss and a FAQ are available on our web site:


Rob Beverly / Mike Afergan

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