>1) Logging into the IMAIL is no longer case sensitive, though it had always >been until now.

This 6.04 note mentions case-sensitive passwords:

http://support.ipswitch.com/kb/IM-20000801-DM02.htm

>2) And most important, we are experiencing delays in the reception of >mails.

what's evidence do you have of this ?

>The SMTP seems to have problems while accepting incoming mails,

if you look in the log file, look at an SMTPD processes from connect to closure and see how long it takes. I don't know of any fast way to do this anaylyis.

>but not while sending them. We noticed that sometimes the spool gets >very big during daytime,

the spool is for "SMTP-" client processes delivering mail, either to remote servers or to local mailboxes.

In the Imail control panel, Queue tab, do you see msgs in teh queue? do they leave when you click send all?

do you see any errors in the log file by SMTP- processes trying to send mail?

How many SMTP processes are running in the NT task manager when mail is slow?

Len