Hi mahadi,
whether you are configuring mailserver with postfix and mysql support in that case you download the change_sqlpass plugin change_sqlpass-3.3-1.2.tar.gz from internet and put that plugin change_sqlpass in the webmail plugin directory and follow these steps.
1. download the change_sqlpass-3.3-1.2.tar.gz
2. put it in webmails plugins directory(inside the squirrelmail folder plugins folder) and extract it by command tar zxvf change_sqlpass-3.3-1.2.tar.gz
3. download compatibility plugin and extract it in wemail plugins directory.
4.cd to the change_sqlpass plugin directory and copry config.php.sample to config.php then edit the file as follows.
i) search for "csp_dsn", at the end of topic include the line
$csp_dsn = 'mysql://username:password@localhost/postfix';
replace uername as postfix database username and password as password of postfix databse.
ii) search for "lookup_password_query" and include the line
$lookup_password_query = 'SELECT count(*) FROM mailbox WHERE username = "%1" AND password = %4';
iii) search for "password_update_queries" and include the below line after $password_update_queries = array(
replace these line 'UPDATE users SET crypt_password = %4 WHERE username = "%1"', with the below line
'UPDATE mailbox SET password = %4 WHERE username = "%1"',
iv) search for "password_encryption" and change the line as below.
$password_encryption = 'NONE';
v) search for "csp_salt_query" and comment the below line as
// $csp_salt_query = 'SELECT salt FROM users WHERE username = "%1"';
and save the file.
4. Go to squirrelmail config directory execute the command ./conf.pl and type 8 you will see change_sqlpass and compatbilty plugins and type the corresponding numbers of both the plugins to install it and save the changes.
5. Login in to squirrelmail page now in options you will see change password plugin and you can change the password.