Startup order for Postfix, Dovecot and Postgrey?

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http://www.linuxquestions.org – My Slackware64 multi-domain mail server is running fine now, with Postfix, Dovecot and Postgrey. One final thing to do is add these services to rc.local, so I don't forget to launch them in case of a (rare) server reboot. The question might be of no importance, but here goes: is there any orthodox startup order for these three services? Cheers, Niki (HowTos)