WARNING: Ignoring deprecated option --unzip

[Jethro R Binks]

On Mon, 26 Jan 2009, Julian Field wrote:

> On 26/1/09 18:23, Kevin Miller wrote:
> > -----Original Message-----
> >    
> > > its really strange that's all, the system is easily managing to
> > > keep up now but telnet to 25 is still really slow to respond,
> > > like 5 - 10 seconds or it'll time out completely.  I noticed my
> > > mailscanner sql db is getting a bit fat so maybe this is causing
> > > some problem...
> > 
> > Getting into the game late here, so maybe it's been asked already, but
> > are you running a caching DNS server on the box?  That may help.
> > 
> > Too, I've seen telnet spin it's wheels when there was no reverse zone
> > for the source (i.e., your) host.  You don't actualy need a reverse
> > entry for your host if you don't have one, but having even a single
> > entry in the reverse zone allows the name server to return a 'not found'
> > almost instantly, whereas it seems to wait to timeout if no reverse zone
> > exists...
> >    
> Yes, that's exactly what I was going to suggest. If telnet 25 produces a 
> long delay before giving a sendmail welcome prompt, it's a *sure* sign 
> of trouble resolving DNS names, as sendmail does forward and reverse 
> lookups on your address to work out who you are before it talks to you.

No ... it's a sure sign of the system producing a long delay.  You cannot 
read any more into it than that, in the generic case.  The system may be 
heavily loaded, or delays might have been artificially introduced as a 
method of shedding spambots cheaply early on.  My own systems delay for 
different numbers of seconds at several points in an SMTP transaction, 
which throws off poorly-written SMTP engines (and ill-configured ones).

But I agree DNS is probably the _likeliest_ cause in this particular case 
...


-- 
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Jethro R Binks
Computing Officer, IT Services, University Of Strathclyde, Glasgow, UK