BLF-CRYPT has been part of glibc for a very very long time. it uses
the blowfish crypt version, that have been changed like 4 times now,
do to issues with it.

I'm not sure why CRYPT wouldn't work for you, seems to work fine in my
dovecot installs.

I'm not sure where the dovecot < 2.0 can use {CRYPT} came from. I'm
using that, since 0.7x? or somewhere around there, all the way up
through, and currently 2.1.7 without issue.

Quoting Sven Schwyn <svoop@delirium.ch>:

Hi

The blf-crypt password schema mentioned in the docs could be a
solution to my auth problem. However, the docs state that actual
support depends on the glibc. Mine apparently doesn't.

Does support depend on the glibc's version (mine is 2.15-r2)?

Maybe someone with access to a box with a good enough glibc could do
the following and post the hash for the plain password "test"?

doveadm pw -s BLF-CRYPT Enter new password: test

With this I could verify whether the BLF-CRYPT scheme would solve my
problem in the first place without going through the hassle of
upping the glibc.

Thanks a bunch!