Re: Strange SMTP Server Behaviour

Giganews Newsgroups
Subject: Re: Strange SMTP Server Behaviour
Posted by:  Ciaran Costelloe (ccostell…
Date: Wed, 26 May 2004

Make sure DNS is set up correctly on both machines, it can give long
timeouts.  To see exactly what is happening, get ethereal (free) which shows
all packets going in & out, and it will display them in real-time also.


"Pierre Roux" <pier…> wrote in message
> I'm writing a mail server using the TIdPOP3Server and TIdSMTPServer
> components.
> When sending a small message, everything is fine, however when sending
> larger messages (approx 1MB or bigger) things starts to go funny.  Outlook
> just sits there for about a minute, and then the message goes through,
> unless a Gracefull disconnect occurs.  All the events are triggered, and
> according to my log mere (milli)seconds apart, but it takes ages for the
> message to leave Outlook.
> Downloading the same message via POP3 takes milliseconds.
> - I've included Sleep(X) statements throughout, thinking it's the old
> Outlook issue.
> - When I step through the code and the whole SMTP process has finished
> except for the disconnection of the socket, the message still shows in my
> 'Outbox'.  The disconnect is triggered long before the message disappears
> from my Outbox (after about a minute or so, message size depending).  At
> this stage, I sometimes get a Gracefull Disconnect, and the OnDisconnect
> does not trigger - which should allways trigger if I understand Remy
> correctly. This is extremely hard to replicate, as you have to send a
> message and wait, and it might not occur.  However, if it does occur, the
> error happens long after the last event in the proccess, and the only
> not showing up in the Event Log is the disconnection.
> Does Indy maintain the state of the TIdSMTPServerThread.SMTPState value?
>  - I'm not touching it, as everything works the way it should on smaller
> messages.
> I have no idea where to look anymore - any ideas?
> What event's code would you like to see?
> I've spent until early this morning on this, and nothing I tried worked
> I'm thinking it might be something environmental/external that plays a
> Small messages, say 2K or so, takes less than 1 second to process.
> I've tried eliminating as many possible environmental problems as
>  - I have Norton Anti-Virus 2003 on my machine, but E-Mail scanning is
> disabled totally, as I was thinking it may play a role in the problem.
>  - Running Indy 9.0.14, Development Snapshot, Delphi 7 on XP Pro
>  - Checked directory search paths as I had Indy 10 on my machine and had
> issue with compiling with some of the wrong files before, but that's all
> fine and fixed now.
>  - Everything runs on the same PC - IP Address & Port is
> At the stage when '[2004/05/26 12:53:26 AM] Message Accepted to User
> Account' is logged into the log file, the message is still in my Outbox,
> well as where it should be in my mail server.
> Log for 7MB file
>  - actually only disappeared from mailbox after about three minutes
>  - Same message took about three/four seconds to download
>  - Looking at the log from start to finish is 13 seconds, yet it was still
> stuck in the outbox long after that!
> [2004/05/26 12:49:37 AM] SMTP Incoming Connection from ireland:3789
> [2004/05/26 12:49:38 AM] SMTP MAIL FROM …
> [2004/05/26 12:49:38 AM] SMTP RCPT TO …
> [2004/05/26 12:49:47 AM] SMTP Message Accepted to User Account
> [2004/05/26 12:49:50 AM] SMTP Disconnected
> [2004/05/26 12:49:50 AM] SMTP Closing Object
> With Gracefull Disconnect:
> [2004/05/26 12:39:37 AM] SMTP Incoming Connection from ireland:3792
> [2004/05/26 12:39:38 AM] SMTP MAIL FROM …
> [2004/05/26 12:39:38 AM] SMTP RCPT TO …
> [2004/05/26 12:39:47 AM] SMTP Message Accepted to User Account
> [2004/05/26 12:41:23 AM] SMTP Error: Connection Closed Gracefully.


In response to

Strange SMTP Server Behaviour posted by Pierre Roux on Wed, 26 May 2004