[notrheadagain]

Personally, I agree emails should be sent in two versions. However, there's a trend of sending just HTML. This article was written some time ago https://litmus.com/blog/best-practices-for-plain-text-emails... and latest comments will also promote the idea of dumping plain text.

Regarding marketing emails, I mean every automated email sequence. Like, you definitely get receipts and stuff over email. And those aren't written by hand.

[dozzie]

Receipt or order confirmation is not (or at least should not be) a marketing e-mail. It's a technicality necessary for transaction.

[notrheadagain]

However, the rule of thumb, especially for drip campaigns, is that you do get some marketing content with almost every email. This could be a specific sign off and such.