I do not have a special program for testing. I test in the real world with real connections.
I have about 450 sites that are connected by the protocol POP3 every 5 minutes. Under this condition, the load on the server virtually none.
You have 450 POP3-Clients connected and you server doesnt slow down at this point???
At some point I send a file to one of the mailboxes and POP3 all of these 450 sites are beginning to answer me. At this point, and there is a large number of sessions since 450 units trying to send and read e-mail from the mailbox.
Just for clarification:
Your POP3-Clients trying to connect to ONE SPECIFIC MAILBOX
at the same time and
Reading and Sending to this ONE SPECIFIC MAILBOX
*What file do you sending to this special mailbox (Large Binary data, pictures ect?)
*How big is the file you sending to your special mailbox?
*Do your 450 POP3-Clients only reading your special POP3-Mailbox or not?
*How do you get informed that any of the 450 POP3-Clients have received the mail?
Have you tried through Mozilla Thunderbird to send a letter? Do you have a delay?
What do you mean with "Letter"? Do you mean a Thunderdbird serial letter or do you
mean a Newsletter sended via PHP-Script or something?
On another thing:
From outside your hMailServer isnt accessible directly (as allready mentioned a few
C:\>dig mx assorti-express.ru +short
telnet mx2.hosting.reg.ru 25
220-relay7.hosting.reg.ru ESMTP Postfix
Shows from outside it points to mx2.hosting.reg.ru or mx1.hosting.reg.ru. In my Thunderbird server i use post.assorti-express.ru
Have all your 450 POP3-Clients post.assorti-express.ru (direct hMailServer) or your Linux Postfix
server configured under Thunderbird->Seversettings->Server name ?