🚀 go-pugleaf

scasterg@magnus.acs.ohio-state.edu writes:
   Someone was recently trying to send mail to my site (not the one I'm
   posting from now) and got the following error messages:
   451 makeconnection: server "smtp" unknown: Invalid argument
   554 saqqara.cis.ohio-state.edu.tcp... 554 System file missing
   Anybody know what that means?

It means that her system uses Yellow Pages (aka NIS); that her
system's "services" map is supported by that means; that her NIS
server was overloaded at the time; and that when sendmail requested of
that NIS server the numeric port number for mail service ("smtp", port
25), the overload on the server caused it not to respond before a
timeout occurred in sendmail, giving the (erroneous) impression of an
unknown "system file."

Solutions:
[1] Add code to retry the getservbyname("smtp") call if it fails.
[2] Hardcode port 25 where the getservbyname("smtp") call currently exists.
[3] Nuke YP/NIS with the biggest weapon you can find.

   She is able to send mail to this account...

Purely an accident.  When she got around to sending mail to you there,
the NIS server was no longer overloaded.  It could happen again any time.

--karl