You may also experience problems even after adding the /etc/pam.d/ftp file.

 /etc/proftpd.conf must be modified for 2 things.

• Change the PAM config file name.
• Allow not valid shell if your ftp users have no shell access.

Change/Add these lines :

# Add this for non shell accounts.

RequireValidShell               off

# Change this to "ftp", above explains to create the file /etc/pam.d/ftp not /etc/pam.d/proftpd 

AuthPAMConfig                 ftp