Exim: Spool file for MSG_ID is locked (another process is handling this message)

When removing spam messages from queue:

Spool file for 1uWOef-00000007Jma-3Nlj is locked (another process is handling this message)
Message 1uWOef-00000007Jma-3Nlj is locked

To remove the message:

Enter the exim directory:

cd /var/spool/exim/input

Find the message ID:

find . -name '*1uWOef-00000007Jma-3Nlj*'

example output:

[root@open input]# find . -name '*1uWOef-00000007Jma-3Nlj*'
./f/1uWOef-00000007Jma-3Nlj-H
./f/1uWOef-00000007Jma-3Nlj-D

and simply delete the messages:

rm -rf ./f/1uWOef-00000007Jma-3Nlj-H ./f/1uWOef-00000007Jma-3Nlj-D

that’s it, its no longer in queue:

exim -bp | grep 1uWOef-00000007Jma-3Nlj