[exim] SMTP protocol violation, 3ware RAID controller

I'm trying to enable a 3ware RAID contoller to be able to send email
alerts through exim4 (a Debian package, 4.50-4), and exim is rejecting
the emails with "SMTP protocol violation: synchronization error (input
sent without waiting for greeting): rejected connection from
H=[127.0.0.1] input="helo qo21\r\n"
I found a previous thread on this list about the same issue with
4.44, which went into a long discussion about RFCs but no solution,
other than some per-host capability to avoid the check was in the
works in a snapshot version. I've tried adding 127.0.0.1 to
local_host_whitelist but it didn't help. Did the funcionality not
make it into 4.50 or is there more to disabling the check than that.
This host only processes mail from localhost, so spambot control is
not an issue. I also realize that the controller's firmware is not
implementing SMTP protocol correctly, but that part of the problem is
unfortunately not under my control (and I would rather that the
limited space in the firmware be used for RAID-related functions
anyway), so I'm hoping to be able to bypass the protocol check in
exim.

Thanks for any advice,
Frank