text is not a problem, as long as it really is text. If your email client (worst offender is MS Outlook, but others are also susceptible) is set to allow HTML to display, then HTML code is run by your computer. You need the latest anti-virus (I use McAfee clinic for about $25 a year) and keep it updated.
attachments can also be craftily malevolent as they can be disguised to appear to be "innocent" attachments like image files (which normally cannot do viral activity) but have "double extension" file names, such as "picture.bmp.XXX", where the "XXX" bit is an executable extension (and there's quite a few of those these days) but is often not seen by the user, depending on how your computer is set up.
The only (hopefully comprehensive answer is to have a "constant virus vigilance such as, per my suggestion above, a regularly updated in-memory anti-virus.
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What Goes Around . . . . .
. . often makes a better landing