QI want to add new field in bugzilla when we create a ticket. can u tell me how can i do that?

QI want to change the email format of bugzilla. how that will be done?

I think you need to modify Mailer.pm. At the very least, you need to specify
a content-type: header of "text/html". And to really do the job right, you
might also appropriately encode characters as HTML entities. You might want
to do the latter piece-wise in BugMail.pm and please take a look at how whine.pl does it..