hosts.allow Question

[Long Story]

Hello everyone,

    Because of the MASS failure tries to connect to my server using random 
passwords
    I decided to allow only my IP to access the server.

   I didnot do this before cuz i was worried this restriction will effect 
any services running..

    a question:
    If i change hosts.allow to accept only my ip adrs and next line is ALL : 
ALL : deny
    is this will effect any performance? such as webmail, smtp or other 
connections/services?
    After fixing those lines, I used the webMail to send mail, then an SMTP 
error came saying
    (access denied) hmm any hint?

    Example (The IP is an Example):
    ALL : 192.168.0. : allow
    ALL : ALL : deny

    One more stupid question.
    If i want to allow a whole class of ips, shall i write as
    ALL : 192.168.0.* : allow        (using the star)
    OR
    ALL : 192.168.0. : allow      (leave it empty)

    Thanks for the help.
    Marwan.

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