Sending email via HF radio is much easier than you might think.
If you know how to set up your radio to use Amateur Digital modes then you are most of the way there with this, I was going to write a guide on how to do this, but there are plenty already on the internet there is a very good guide to set up an Icom 7300 for Digital Mode operation here (the settings on the Icom 7100 are the same).
The software you need is called winlink. And it works without the need for an expensive modem, all you need a soundcard interface. Many of the newer HF Radios (eg Icom 7100, Icom 7300, Yeasu FT991 etc) already provide this and you can connect them to your PC with a USB cable.
Once you have installed the winlink software simply select your radio in the Radio setup, select the appropriate sound card and connect. There is a very good guide on how to set up winlink here.
When you are set up you can send a position report to winlink when you are out and about and plot it on a map. heres mine:
Map Courtesy of winlink.org. Copyright Amateur Radio Safety Foundation, Inc., a non-profit, public benefit corporation.