In the following, the detailed effect of checkbox Activate parallel processing on the processing sequence is shown. See sections POP3 (Mail), IMAP (Mail) and X.400 (mail).

Checkbox is not set

In this case, each mail is handled as follows.

The email is picked up (and deleted if applicable).
A job is started for the responsible processing profile.
After the termination of the processing profile (successful or not), the next email is fetched.

Checkbox is set

In this case, each mail is handled as follows.

The email is picked up (and deleted if applicable).
A job is started for the responsible processing profile.
The next email is fetched immediately.
So the fetching is much faster, but the processing is asynchronous. That is, the emails may overtake each other during processing unless the checkbox Profile may only run in one instance is set in the processing profile.