Outlook VBA-Extensions
Simple Outlook VBA Script which adds the mail received date in the subject line of a MailItem. Adds the date to all selected mails. If a slected item isn't a MailItem (e.g. MeetingItem / Calender-Entry) then a counter increase an displays a Message Box to the user.
You can sign your VBA-Script with a digital certificate. Office provides a easy way to create a user based certificate with the "SELFCERT.EXE" tool in the Office root directory e. g. C:\Program Files\Microsoft Office\root\Office16\SELFCERT.EXE
After the creation of the certificate you can sign your code directly in Outlook "Tools --> Digital Signature..."
You can find more under the following link: https://support.microsoft.com/de-de/office/digitales-signieren-eines-makroprojekts-956e9cc8-bbf6-4365-8bfa-98505ecd1c01