My dad mentioned the letter for the first time to me a couple of years ago. I had already been a full-time writer for several years by then. It’s kind of a long story, but my parents were very strange. He said something in passing about me being a writer saying, “Well, I guess it makes sense that you like writing after what your college professor said.”
That caught me off guard. As far as I knew, my parents had never had any contact with any of my professors. When I asked what he was talking about my dad told me about the letter and how they had thrown it away because I didn’t need to see it. (Maybe I should write about this full story sometime.)
As far as email writing guides, I have not found anything I love. I have mostly used classic copywriting techniques combined with some research about things like spam triggers and ideal subject line length. I test everything and over the years have developed my style and techniques from that.
Copyblogger.com used to have a lot of great stuff about emails that I read and absorbed. I’m not sure if it is still on their site or not, but it’s worth searching their archives.
One thing I would avoid is the email course by AWAI — it’s super expensive and not very useful.
I write a Medium story a while about writing cold emails to land freelance clients. that might be useful:
How to Write Cold Emails That Land Profitable Freelance Writing Clients
From subject line to sign-off, a foolproof guide to help writers craft effective cold emails
I have a partial draft of a small business email marketing guide that I think about finishing every few months. Maybe, it’s time to go back and look at it again…
Sorry, I can’t be more helpful.