question about .procmailrc

[galili assaf]

Hello all,
I am using spamassasin in .procmailrc (unix account).
my question is about .procmailrc:
is .procmailrc synchronized? I mean, if two new mails are coming to my accout, 
will the first .procmailrc script execution finish before the second execution 
will start?
I am trying to do something so the order is very importent.
Thank you,
Asi