Standard	Portable
Multiple Users:	Yes	No
Can move between computers:	No	Yes
Can change edition easily:	Yes	Yes
Download:	Download	Download

You can also see a feature-by-feature comparison between the different versions.

As you can see, the only major difference between TrulyMail Standard and TrulyMail Portable is that TrulyMail Portable is designed to be put on some removable media (like a USB drive) and moved between computers (like home, work, Internet cafe, etc.); therefore, the portable version does not support multiple users. The portable version can be installed on your computer's hard drive - there is no requirement that it gets installed on a USB drive.

 TrulyMail Standard is designed to be installed on one computer and can be used by all users of that computer. This is helpful if you have multiple people using the same computer (with different Windows logins) who all want to use TrulyMail.

Do not worry, though, you can easily move your data to the other edition if your needs change in the future.