Can we change the notice period in this way? Circulated an internal note regarding this via Email.

I have a query, In my company we want to change the official notice period from one month to 3 months,
We have circulated an internal note regarding this via Email. Can we change the notice period in this way?
Or Should we issue individual letters, viz., an addendum to the appointment letter with the reference of a clause in the appointment letter and seek each one's acknowledgement?

Please help at the earliest.

Hi,
Changing the official notice period typically requires an amendment to the employment contracts of the affected employees. It's important to ensure that the change is communicated clearly and that employees have the opportunity to acknowledge and agree to the new terms. While circulating an internal note via email is a good start, it's advisable to issue an addendum to the appointment letter referencing the specific clause being amended and seek each employee's acknowledgment. This helps to formalize the change and ensures that all parties are aware of and agree to the new notice period..
Regds

Thank you so much for a prompt reply...