$File = Get-childitem "\\servername\folder\file.txt"
if ($File.Length -gt 10000) #change here to adjust your file threshold
#if condition is true .....
# new commandlet in V2 send-mailmessage
send-mailmessage -to "User01 <user01@example.com>" -from "ITGroup <itdept@example.com>" -cc "User02 <user02@example.com>" -bcc "ITMgr <itmgr@example.com>" -subject "Don't forget today's meeting!" 
#if condition is false .. do noting ....