At 17:54 5/2/2005 Monday, Dave wrote:
>We continually get reports from users that they are missing some posts. The
>problem is intermittent and there is no obvious pattern.
>
>There are no indications in the LISTSERV or LSMTP logs that delivery failed
>to these users.
>
>I was quick to blame the problem on the receiving users (local spam filters,
>etc.) but that excuse is wearing thin. They claim they have no problems
>receiving E-mail from other mailing lists.
>
>Are there any known issues with LISTSERV and delivery to certain remote
>systems? What could explain this intermittent behavior?

What actually controls or alters delivery of email (forget about LISTSERV for the moment)?

Off the top of my head:

x  a "client" SMTP (typically selected by the LISTSERV(s))
x  the Domain Name System (multiple DNSes, which may or may not be in-sync)
x  SMTP "MX" servers (some may be multiple, and not identically configured)
x  routers (and their level of maintenance code)
x  mail redirectors
x  security/authorization systems availability
x  site anti-spam filters (well or ill configured)
x  user anti-spam filters

Add onto that, the LISTSERV Distribute Backbone which makes "decisions" on which LISTSERV host sites used to deliver (and uses many of the types of systems referenced above BEFORE getting to the end user site).

Some of these tend to have a time-of-day involvement as systems reboot/backup in the evening and active lists generate mail 24x7.  This has frequently been the source of  intermittent delivery problems. 

With some anti-spam systems now configured NOT to bounce "bad" e-mail, then tend to just throw it away without further user or system admin involvement.


/Pete Weiss
independent list consultant