[wplug] SMTP delay

[duncanhutty at comcast.net]

Postfix.
This sounded like a promising avenue of investigation. I do not have a local DNS server here, the box is configured to use the ISPs DNS. Presumably when my local client attempts to connect the (local) IP address cannot be resolved with reverse DNS.
However, when I sent mail to it from an external source, I still saw a 17s delay between client connect and client disconnect, and the log entry was:
Aug 24 12:06:05 mail postfix/smtpd[29952]: connect from sccrmhc11.comcast.net[204.127.202.55]
so reverse DNS was working for that client.
I shall increase the logging and look into this again.
Duncan Hutty

-------------- Original message -------------- 

> > From: "Wise, Jeremey" 
> > Date: 2004/08/24 Tue AM 09:41:13 EDT 
> > To: General user list 
> > Subject: Re: [wplug] SMTP delay 
> > 
> > I would second this. I have a Pentium 133mhz with 40MB RAM running ten 
> > users SAMBA, Mail, Web and it runs fine and has been for about four 
> > years now. 
> > 
> > On Mon, 2004-08-23 at 20:25 -0400, Bill Moran wrote: 
> > > duncanhutty at comcast.net wrote: 
> > > 
> > > > I am testing a mail server and have been told that even an old k6II 500 
> > > > with 320MB should be able to cope with so many zillion messages a month 
> > > > with no problem even with LDAP and spamassassin. 
> > > > When I (handwavingly) test this setup, sending a single, tiny message, 
> > > > it takes about 15 seconds to 'finish' transmitting the message to the 
> > > > mail server (on the LAN). I am calculating that time from monitoring 
> > > > Outlook's send and receive dialogue box. 
> > > > When I test from the same machine to my ISP's mail server (obviously 
> > > > NOT on the LAN), the same message takes <1s to transmit. 
> > > > Trying to eliminate error and check my testing, I made sure that there 
> > > > was no other traffic/activity on the server. I monitored 
> > > > /var/log/mail.log and saw 16s between the client connecting and 
> > > > disconnecting. 
> > > > Seems to me like 16s is a long time for a 1k message even on a vintage 
> > > > PC like this. Are my expectations out of whack? 
> > > > Or should I be expecting better performance and investigating why this 
> > > > is so slow? 
> > > > If I move the LDAP server to another machine, would I expect better 
> > > > perfomance? I would think that network vs. localhost lookups would be 
> > > > slower, but maybe removing the cpu cost to another cpu might help. 
> > > 
> > > The potentialtech.com mailserver is only an 800mhz and it's also our 
> > > HTTP and DNS server. I see no such delays on it, so I can't imagine 
> > > that it would take a 500mhz 15 seconds to transmit 1 email. 
> > > 
> > > It sounds suspiciously like a timeout. Are you sure the DNS is working 
> > > as the mailserver would expect? I've seen more network problems boil 
> > > down to a program trying to do a reverse DNS lookup and timing out. 
> > > What MTA are you using? Can you increase logging to determine exactly 
> > > where the 15 seconds is occurring? I mean, is it between the HELO and 
> > > the DATA? Or is it after the last line of the DATA has been transmitted? 
> > > This might give a clue as to what the holdup is. 
> > > 
> > > I can't imagine any legitimate reason why that machine would take so long. 
> > > 
> 
> I agree with Bill (I think) that is seems like timeout. Most likely DNS. Is 
> this box connected to the Internet? If so, let us know. We can try connecting 
> to your box. What mailserver (MTA) are using? Are you using your ISP's DNS 
> server? 
> 
> Chris Romano 
> 
> _______________________________________________ 
> wplug mailing list 
> wplug at wplug.org 
> http://www.wplug.org/mailman/listinfo/wplug 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://penguin.wplug.org/pipermail/wplug/attachments/20040824/c3b6e2e5/attachment-0001.html