Viewing a plain text email you could see the complete headers displayed as
the message body (but with no carriage returns) and you cannot see any of
the actual message body.
Probably you have a MMCache PHP accelerator running.
If so, the temporary files were not correctly deleted the last time
when Apache terminated and these files should be cleared out every time
when Apache restarts.
In this case you have two options.
1. Disable caching to disk. It could be done by using mmcache option shm_only.
However, if there are scripts which are too big for caching then they will not be cached at all.
/etc/php.ini or /etc/php.d/mmcache.ini
mmcache.shm_only = 1
2. Change the Apache start-up script to clear the mmcache
caching directory at every Apache start / restart.
The following mmcache option defines cache directory:
mmcache.cache_dir = /var/cache/php-mmcache
3. You can apply mmcache.filter to determine which PHP files must (or must not) be cached.
mmcache.filter = "!*message.php*"