For what it's worth & because it's easy to copy, here's the list in Agent's help screen.

AFAIK As far as I know
AUORFA alt.usenet.offline.reader.forte-agent
<BG> Big Grin
BOFH Bastard Operator from Hell
<g> Grin
BRB Be right back
BTW By the way
CP Copy protection
FRE Frequently requested enhancement
FUBAR Fouled up beyond all recognition (or repair)
FWIW For what it's worth
FYI For your information
GD&WVVF Grinning, ducking, and walking very, very fast
GR&D Grinning, running, and ducking
IAE In any event
IANAL I am not a Lawyer
IMHO  In my humble opinion
IMO In my opinion
IOW In other words
LOL Laughed out loud
LZ Loser!
OIC Oh, I see
OTOH On the other hand
PITA Pain in the A$$
PMJI Pardon my jumping in
PMFJI Pardon me for jumping in
ROFL Rolling on floor, laughing
ROTFL Rolling on the floor laughing
ROTFLMAO Rolling on the floor laughing my a$$ off
RSN Real soon now
RTFM Read the f@%# manual (or message)
SNAFU Situation normal, all fouled up
TIA Thanks in advance
TPTB The powers that be
TTFN Ta ta for now