What's the hardware configuration of your server? If it's underpowered, sure, it'll take awhile to process. Since viruses are rejected immediately, you won't be able to accept messages and process them later.
Personally I wouldn't run SME 7 with virus & spam filtering enabled on less than a Pentium III/450 with 256 megs of RAM.
If outgoing SMTP is a big problem, bypass the transparent SMTP proxy in the email settings and route from workstations directly to your ISP's SMTP server.
And you should upgrade to RC2.
And everyone who answers questions here volunteers his or her time, so you have no right to expect anything.