Files with etf suffix can be found as old e-mail messages in Enriched Text format. It was used before HTML replaced it as main format for electronic communication.
There are 2 other file types using
the ETF file extension!
.etf - PolyEdit file
.etf - Enigma Transportable file
ETF file extension - Enriched Text Format e-mail message
What is etf file? How to open etf files?
File type specification:
The etf file extension is related to Enriched Text, a formatted text format for e-mail, defined by the IETF in RFC 1896.
It was "intended to facilitate the wider interoperation of simple enriched text across a wide variety of hardware and software platforms". Today, enriched text is almost unknown in e-mail traffic, while HTML mail is widely used.