calendar modify is creating a new appointment

Hi experts,

I have a custom program which is creating appointments in SAP and then sending mails to outlook.

After appointment creation in SAP via my program, when I update it and check mails in my outlook, it is faulty.

Same calendar appointment is not getting updated but a new calendar appointment is created with modified details.

Also, in SOST when I check emails, I see UID for appointment is different in both of them. This also clarifies that a new appointment is created after update.

Please help, it is urgent.