Dear All
Recently I noticed when account is created (D7), Drupal send a welcome mail to user  (mode is no_approval_required),

the format of the mail is something like this ..

user,

Thank you for registering at <site>. You may now log in by clicking this link or
copying and pasting it to your browser. Please set your password accordingly.

<link> username: user -- <site> team

This was working fine till recently.  Then I have written a custom module to send group mails. It is very simple, reads all mail ids from a table and send mail one by one just making use of PHP's inbuilt mail function.

Then I noticed, all the yellow colored text above goes blank when Drupal sends mail to user. 

On further debugging found that, in function _user_mail_text (in user module), the variables site::name and user::name are blank.

Did anybody face this kind of issue anytime?
Kindly give me some pointer how to approach to fix this issue.

Thanks
Kamal
Net Cloud Systems