SubD25                RJ45
DTR 20 ----------------- 1
CTS 5 ------------------ 2
GND 7 ------------------ 3
RXD 3 ------------------ 4
TXD 2 ------------------ 5
GND 7 ------------------ 6
RTS 4 ------------------ 7
DCD 8 ------------------ 8 

Without RTS/CTS/DCD/DTR:

SubD25                RJ45    
GND 7------------------- 3
RXD 3 ------------------ 4    
TXD 2 ------------------ 5      
GND 7 ------------------ 6    

Ground on RJ45 Pin 3 is probably needed on both pinouts.

From Martin Etteldorf (original source from Motorola).