Some filtering actions must be used very carefully as they have the potential to cause serious problems.
Both scanning and actions can execute applications. It is very important that applications do not run for long periods of time with many instances running simultaneously as this can use up a lot of CPU time and cause your server to slow down considerably. Scanner application executions are only supposed to run for very short periods of time and then close, returning a value that can be used to indicate any infections. If the application does not return for a considerable length of time, it will be terminated and the file will be indicated as infected to be safe, possibly causing uninfected mails to be changed or deleted. The long wait for the application to close can also cause congestion in the Antivirus Filtering queue holding up all other mail passing into the system, eventually resulting in mails being discarded.
Some actions can cause new files to be created. It is very important that this is moderated and set up with care as this could potentially lead to very large amounts of hard drive space to be used over a long period time resulting in hard drive space possibly even be used up completely, stopping your mail server from continuing to function properly.
New Mail Creation
Some actions can cause new mails to be created. It is very important that actions are not set up such that extremely large quantities of new mails are created unnecessarily and not noticed or removed from the system.