\unprotect
\startsetups[letter:backaddress] \def\\{\lettervalue{\c!backaddress\c!separator}} \doifelselettervalue\v!backaddress {\lettervalue\v!backaddress} {\lettervalue\c!fromname \doiflettervalue\c!fromaddress\\ \lettervalue\c!fromaddress} \stopsetups
\protect
And add \setupletterstyle[backaddress=yes] to your file because the backaddress is disabled by default.
Thanks very much, this works! Still a minor suggestion regarding the interface: I guess at the moment it's slightly inconsistent because on the one hand one has \setupletterstyle [backaddress=yes] and on the other hand \setupletter [list={name,phone,fax,date}] Note that both commands actually implement boolean switches, namely, whether backaddress, name etc. should be displayed or not. For consistency reasons these switches should perhaps be interfaced in the same way, e.g. by "name=yes" etc. Another possibility would be removing the "backaddress=yes" switch completely. Then if backaddress data is supplied it's printed along with the line below and if not, well, then leave out the separator line. What do you think? Oliver