cannot send email to certain webmail from my local sendmail server

if you ever faced a problem that you can't send emails from your local sendmail's server to certain webmail.. and you're likely the person that i listed here

1. you're using linux, ex: ubuntu,centos etc

2. you installed sendmail as your smtp server

3. you're successfully sent emails to yahoo and gmail account from your command line interface. ex:

root@linux-box:/#sendmail someperson@yahoo.com 
result: success&arrived! user@localhost.localdomain

4. unfortunately you cannot send to certain webmail.

ex: sendmail someperson@somedomain.com 
result: failed!

5. you're going to forum & irc for help => they mock you as a kiddy and shoooh you to go once again to google.com. ex:

"hey kid please find gud linux books & read it back!! search uncle google you're lazy bones!!ya don't really understand open source da u??" (actually even they don't know the answer!)

6. worry no more.. i think this is a solution for you...

masquerade your local domain! so when you send emails it wont show like :  user@localhost.localdomain but it will show as user@somedomain.com.(in /etc/hosts you can see what your local server is => localhost.localdomain)

only then that certain webmail won't reject you're email anymore.(hope so)

1.go to: /etc/mail/

2.create one file, you can call it anything ex: genericstable

put usernames that you're using ex:

root root@somedomain.com

user user@somedomain.com

note:you can spoof your mail address

3.open your /etc/mail/sendmail.mc

and put this thing inside it:

FEATURE(masquerade_envelope)dnl

FEATURE(`genericstable')dnl

GENERICS_DOMAIN(`localhost.localdomain')dnl

4. finally compile it from your shell: make -C /etc/mail

5. restart sendmail: /etc/init.d/sendmail restart

6. testing to send to your targeted webmail:

sendmail someperson@somedomain.com

7. please don't send spam to your friends (although you're anonymous) bcoz they can detect you by reading the headers