Writing is the main way I do Psychotherapy Online - of course there are options to use Video and Audio but that is not my approach as I like text and writing. Photos and images are a way to add Art Therapy into the mix. All of this requires email. Managing mail is certainly one of the arts for an online therapist. When you do psychotherapy online it may also be a good time to do some email housekeeping.
Here are some ideas but not prescriptions, everyone has their own style & that is fine!
Here is an excellent document: A Beginner's Guide to Effective Email by Kaitlin Duck Sherwood, it is about such things as lay-out and quoting. The guide does not does not mention HTML mail - it is all about plain text mail. I use plain text mail and while it makes the emails less "pretty" they are easier to quote, search, store, cut and paste from and less virus prone. There will be an option in your email program to switch to plain text.
Make a folder in your email program for the psychotherapy and keep the mail, sent and received in that place. You can sort the emails by date, or occasionally by subject line. Such a folder could be kept online using a web-mail service described here.
Documents and Images
You may have photos, drawings or written documents. Keep those close to hand in their own folder - physical or on the computer.