geakazoid пишет: I tried to install the acSMTP however I cannot de-compress rar.

See www.rarlab.com. RAR version 3.x uses new compress features but requires version 2.9 or higher to decompress archives.

geakazoid пишет: Will the acSMTP and POP replace the current smtp.exe and pop.exe?

I don't understand what you mean. If it is about smtpsend(3) and pop3recv then no. This is a new (beta) version of SMTP/POP/IMAP server that use current versions of smtpsend.exe and smtpsend3.exe to deliver mail to outside users. Currently, it doesn't support mail collection from external POP3 mailboxes.