🚀 go-pugleaf

I posted a problem (?) a few days back to d.i.s.pc about problems
I have experienced recently sending mail using ka9q (2.16d) and
from the underwhelming response (thanks Ian!) suspect that the
cause is at my end, not Demon's.  The reason for the post here is
to get (I hope) some wisdom from those who know the software well
so that I can fix/workaround the problem.

A tiny bit of background: I have no troubles receiving mail and
news, nor (to date) of posting news; ftp and telnet seem to work
fine (though a friend has had a problem logging in to my ftp
server with a specific password, as opposed to '*' in FTPUSERS).
This leads me to believe that my configuration is basically sound.

The question therefore is essentially this: what effect (if any)
does the size and/or number of files in ~/spool/mqueue have on
SMTP performance?  My observations are that one ot two small
messages are accepted quite quickly, but that 5 or more largish
files (eg. 5 x 50k) do not move *at all*.

I have looked through smtpcli.c and smtpserv.c for 'hints' on
ways one might reconfigure or use ka9q, but nothing is startlingly
obvious (these sources 1.18 and 1.13 respectively from ka9qsrc.zip
though I don't know if these are the live versions).  Not really
surprising as I am no IP wiz :-( but ever the optimist...

Any light that someone might shed would be greatly appreciated.
And if someone has worked out how the 'smtp wait 20' command
works (or doesn't...) I'd love to know too.

My apologies if this is off-topic in d.i.d - it's the first time
I've posted here.
--
Pete