mboxrd was invented by Rahul Dhesi et al. as a rationalization of mboxo and subsequently adopted by some Unix mail tools including qmail.

All these variants have the problem that the content of the message sometimes must be modified to remove ambiguities, as shown below, so that applications have to know which quoting rule has been used to perform the correct reversion, which turned out to be impractical. Using MIME and choosing a content-transfer-encoding that quotes "From_"