I just bought a x4270 lexmark.i do not see in the

Yes, you can.

You have to connect the answering machine to the X4270 like this

http://www.lexmark.com/publications/pdfs/2007/4200/ug/en/basics.html#wp633882

and set it to answer before the X4270 does. Say, 4 rings for the answering machine and 5 for the X4270.

The X4270 will monitor the few first seconds of the call anyway, and if it detects the whistle of an incoming fax, it will disconnect the answering machine and receive the fax.

With most answering machines, disconnecting while the greeting message is still playing will not be considered a call.