Recipient receiving same emails many times

It happens that when you send email, the recipient receive the same email many times in period of intervals. It is because of exim database corrupted and also you receive following error in exim_mainlog.

Berkeley DB error: /var/spool/exim/db/retry: unexpected file type or format

Apply following solution to fix this issue.

Stop exim service using following command

/etc/init.d/exim stop
or
service exim stop

then go to /var/spool/exim/db/ and remove all the files. Make sure to take the backup of /db folder if in case if there is another problem arise. 

Start Exim service.

/etc/init.d/exim start
or
service exim start

After starting exim service, It will rebuild exim database.