Someone

#!/bin/bash

FILES="
/var/log/file.log
/var/log/exim/mainlog
/var/log/exim/rejectlog
/var/log/auth.log
/var/log/httpd/domains/domain.com.log
/var/log/httpd/domains/domain2.com.log
/var/log/httpd/domains/domain3.co.uk.log
"
rm output.log

for file in $FILES
do
	if [ ! -e "$file" ]	# check if the file exists
	then
		echo "$file does not exist." ; echo
		continue
	fi
		tail --lines=25 $file >> output.log
done