Plaintext parts of email are fading away (in spam and non-spam)
One of the things that I've been noticing these days is how much plaintext parts of emails are fading away. I'm not talking here about HTML-only emails (which have been on the rise here for years); instead, this is about MIME multipart/alternative email which theoretically has both a plaintext and a HTML portion. For years I've had my mail system set to show me the plaintext version instead of the HTML version. For a long time that worked reasonably well, but increasingly it's not; when there is a plaintext version that isn't just 'get a HTML capable client', more and more often the plaintext version is incomplete or otherwise not really functional.
This happens in regular email and it also happens in spam email. For instance, my spamtraps recently captured some email where the plaintext portion started:
To view it online, please go here: %%webversion%%
That's the literal text, and it comes from a spam operation that's clearly organized and using dedicated software (and servers) for their spamming.
Of course, plenty of spammers still use plaintext or functional multipart messages; it seems to be especially common with advance fee fraud spammers, who generally have plain text messages anyway and who may be using well implemented webmail software that does this right. But if spammers (and significant mailing list operations) cannot be bothered to even look at their plaintext versions and get them functional, I have to conclude that plaintext versions are becoming vestigial remnants in the modern email ecosystem.
This isn't surprising, really. If anything it's sort of surprising that it hasn't happened before now. Apparently inertia is a thing.
Unfortunately, since this is done by both spam software and legitimate senders, a significant mismatch between the plaintext version and the HTML version is probably not a useful sign of spam. Depending on your tastes and who you get email from, it may still be a useful sign of email you don't want to read.