- Spam with no message body
- Spam containing replaceable tokens, such as $TO or %%USER_EMAIL%%
- Spam with a subject of "subject" and a body of "body"
I'm not sure if all of the spam I get that doesn't advertise any sort of product or service or website, and it just a bunch of nonsense words or sentences, is trainee spam. I'd guess that it's more likely to just be probing to see if my address is real. But the examples I listed above must be spam sent by people who are just learning how.