In the following, the detailed effect of the Activate parallel processing checkbox on the processing sequence is shown. See POP3(S) (mail), IMAP(S) (mail) and X.400 (mail).
Checkbox is not set
In this case, each mail is handled as follows.
The e-mail is picked up (and deleted if applicable).
A job is started for the responsible Processing profile (see Distribution rules (mail)).
After the termination of the processing profile (successful or not), the next e-mail is fetched.
Checkbox is set
In this case, each mail is handled as follows.
The e-mail is picked up (and deleted if applicable).
A job is started for the responsible processing profile.
The next e-mail is fetched immediately.
So the fetching is much faster, but the processing is asynchronous. That is, the e-mails may overtake each other during processing unless the checkbox "Profile may only run in one instance" (see General (Main settings)) is set in the processing profile.