It's sounds like you're using a fixed-width font (like courier) that is typical to a terminal session and relying on it to line up you data nicely. And for those instances it works fine. Also if a user defaults their mail reader to use a fixed-width font.
The problem is then you send your message to someone that uses a GUI tool (like outlook, or a web-mail client, or many others) that uses proportionally spaced characters, so an '1' takes up less space than an '0' (for example), and then you get something that is ugly.
If this is for a corporate project and the range of supported mail readers is limited, you should be able to "wrap" your report in and specify a fixed-width font. Even in a corporate organization, this can still not be perfect AND if your user base is more general, then it gets more difficult to make sure everyone gets a perfectly formatted report. Maybe you need to add some qualifications like "best formatting presented when using xxx mail reader".
You can post to http://webmasters.stackexchange.com/ here and ask for advice on simple HTML formatting that has a high probability of a correct rendering.