Jens Vagepohl wrote:

what happens is that standard error message gets called whenever someone authenticates for the first time, meaning whenever they get the username/password popup. even though you never see the rendered standard_error_message its code gets executed.

That makes sense. So if i put my sendmail tag inside the standard_error_message, but outside of any <dtml-if> construct, i should get email everytime anybody does a login, isn't it? I checked this and yes, that is correct ;) But this is new, isn't it? Jerome Alet wrote:

Are your MailHost instances using the same SMTP host whatever Zope server you test on ?

Yes.

Could you try to send a message from each host using the MailHost code outside of Zope and see the result ? (I don't know if this is feasable or not, however)

I dont understand everything of the question. There is only one host. I have used Python 2.2 code (with smtplib) before from my winnt 4 machine to do a mailing. It was without problems. But this is not the mailhost code. Do you mean: directly in python something like: import mailhost and figure out from code what to do? Probably this is what Chris tries to explain with the pdb message? Jens wrote more:

your standard_error_message tries to send mail and that's where the DNS lookup stuff comes in. i have to second chris in his opinion that this is due to DNS lookup problems on that particular machine.

Ok. Yes, sending an email with <dtml-sendmail> cost in both 2.4.3 and 2.5.0 about 20 seconds on the two NT machines. So i have DNS lookup problems that became the cause of the slow authentication popup box, Chris was right from the start. Chris advised me to try the debugger. I'll do that, it's new for me. But at the moment i am terribly tired. Thank you for all of your interest and help. You are helping even when you think it is a somewhere DNS-configuration error and not a Zope problem!