Hi @SenhorDolas,
Welcome to the Microsoft Technical Support Forum.
Based on your description, resetting passwords and applying password policies won’t directly impact Exchange Server functionality. However, ensure that users update their credentials in any email clients (such as Outlook) after password changes.
Additionally, consider enabling Modern Authentication in Exchange Server 2019 for enhanced security. Modern Auth allows users to authenticate using ADFS and access tokens.
Remember to test any changes in a controlled environment before applying them to production. If you encounter any issues, you can fine-tune the policies as needed.
Please feel free to contact me if you have any queries.
Best,
Jake Zhang