Code to Show E-Mail Details
 

If you would prefer to always have email details visible, instead of clicking the "show details" button, add this code to your stylus sheet:

.v-Message-details {
height:auto !important;
}
.v-MessageCard-toggleDetails {
display:none !important;
}

The standard method of doing this is changing the style sheet at the server, by choosing the Classic theme. See:
https://www.fastmail.com/help/guides...n.html#headers

As described in the Help, this also changes a few other things in the display.

Bill

Thank you, Bill, that is very helpful.
I'd not realised that 'themes' could change behaviour like that - I thought they were merely cosmetic.