All macros are part of the VBAProject.OTM file. They aren't stored
individually and there is no easy way to distribute macros. If you
distribute the entire project file and replace the current one for
each user that would work but would replace any macros that the users
currently have. In addition, unless macro security is set to Low the
users would be prompted to enable macros each time they start Outlook.
Low security is a major risk, and you can use High security only with
signed macro code, which means installing the signing certificate on
each user's computer and having them sign the macro code with it.
The preferred way of distributing code is to write the code as an
Outlook COM addin and to distribute that.