[exim] Heads up: Beware pipelining + delay command

So I include a little 20s delay command at the end of my acl_rcpt_to. (Why
there? Because I don't include the delay if the recipient is postmaster or
abuse.) No worries, right?
Until I discovered that if pipelining_advertise_hosts is set to all (as per
default) and the sending server is pipelining to 3 users, there's no
response until all three delays have occurred-- and in this case 60s was
enough for the sending server to timeout.

Now, the sending server SHOULD have a 5 minute timeout, but (a) this
particular form of remote brokenness is not uncommon and (b) even if the
remote timeout was correct a 15-recipient message would have broken it.

I resolved it by turning off pipelining to remote hosts, which was a quick
fix, but just wanted to make others aware of this potential pitfall. This
was Exim 4.6.3 running on Mac OS X, but I imagine it's common to all
versions of Exim.
--
Dave Pooser
Cat-Herder-in-Chief, Pooserville.com
"...Life is not a journey to the grave with the intention of arriving
safely in one pretty and well-preserved piece, but to slide across the
finish line broadside, thoroughly used up, worn out, leaking oil, and
shouting GERONIMO!!!" -- Bill McKenna