Do you know the 'root' or 'admin' password for your SME server? (Answer 'yes' 'or 'no', don't post the password here...)
Do you know what version of SME you are running?
Do you have any way to contact your administrator? Most SME administration can be done remotely...
Is there a computer in the office that your administrator normally uses when working on the SME box? If so, it may have putty installed, and may be configured to connect to your SME without using a password...
Has email stopped flowing in both directions (in and out), or can you still send email?
If you don't have the root/admin password and can't wait until the administrator is near a computer you'll need to change the root password. Here is a link to a discussion of how to do this, but you'll want to be very careful!
http://forums.contribs.org/index.php?topic=34286.0Many of the posts about SME refer to the SME command prompt - to get there you can login using the keyboard & monitor physically connected to your SME server, or download 'putty.exe' from
http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html (for windows systems), or open a terminal window and use 'ssh <smehostname-or-ipaddress>' on a Mac... All three of these methods allow you to login as 'root' to execute various diagnostic commands -- but you need to know the root password first...