Alter pending approval mail body and use another mail engine instead of drupal mail

Hi,

I have used logintoboggan for to extend registration functionality. I am facing issue with mail. In my system I am using sailthru for to send emails which is working properly with other mails.
When any user register to our system there is one welcome mail has been sent to user with subject : " Account details for [user:name] at [site:name] (pending admin approval)" and

Body : "[user:name],

Thank you for registering at [site:name]. Your application for an account is currently pending approval. Once it has been approved, you will receive another e-mail containing information about how to log in, set your password, and other details.

-- [site:name] team". we can this setting from our backend.

But when we are use logintoboggan module this body has been altered via alter mail hook function with this texts;"The user has automatically received the permissions of the LoginToboggan validating role. To give the user full site permissions, click the link below:\n\n!validation_url/admin\n\nAlternatively, you may visit their user account listed above and remove them from the validating role."

as well as above body is send via drupal mail.

I have also make one module for to alter this body and its working for all other mail which is send via sailthru but its not working for this single mail and its using simple drupal mail for mail sending.

so, Please guide me how can i resolve this issue.

Thanx & Regards

Dhaval Panara