PSKmail needs a special version of gMFSK which:

For the Client:
* transmits a file gmfsk_autofile as soon as it sees one in your home directory

For the Server:
* transmits a file gmfsk_autofile as soon as it sees one in your home directory
* transmits always at 1000 Hz
* limits AFC to 985 - 1015 Hz

You can switch the function of this version of gmfsk to:
* Client: by putting a file 'PSKmailclient' in your home directory
* Server: by putting a file 'PSKmailserver' in your home directory

If none of those files are present gMFSK reacts normally.

You can copy this binary over the 'normal' version in /usr/local/bin
(cp gmfsk /usr/local/bin) after you installed gMFSK-0.6 the normal way.