[Exim] SMTP Authentication with mysql database..

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Password in mysql database are in the format of md5_base64 using ( Digest::MD5 qw(md5_base64) module). Can anybody tell how to autheticate it from the EXIM...

I tried the given piece of code...but it is not working

######################################################################
#                   AUTHENTICATION CONFIGURATION                     #
######################################################################

# There are no authenticator specifications in this default configuration file.

login:
  driver = plaintext
  public_name = LOGIN
  server_prompts = "Username:: : Password::"
  server_condition = "${if and { \
                        {!eq{$1}{}} \
                        {!eq{$2}{}} \
                        {crypteq{$2}{${lookup mysql{SELECT password FROM mailbox WHERE mailbox_name='$1'}{$value}fail}}} \
                        } {yes}{no}}"
  server_set_id = $1

# End of Exim configuration file

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