I'm not sure it matters more that you're using a Pi than it would matter which old laptop you're using.
And, when it's as low-level as simply making something work, rather than particularly optimising it (when the fact that it's a Pi or a 2003 T61 or a whatever do matter), I think that treating it as a slow Debian machine and finding a generic howto (or, better, a few generic howtos) is much more appropriate than insisting that you find a "How to install postfix and courier on as raspberry pi".
Obviously for troubleshooting problems the hardware's much more important, too, but so far I've just treated my Pi as just another Debian box and everything's just working.
And, when it's as low-level as simply making something work, rather than particularly optimising it (when the fact that it's a Pi or a 2003 T61 or a whatever do matter), I think that treating it as a slow Debian machine and finding a generic howto (or, better, a few generic howtos) is much more appropriate than insisting that you find a "How to install postfix and courier on as raspberry pi".
Obviously for troubleshooting problems the hardware's much more important, too, but so far I've just treated my Pi as just another Debian box and everything's just working.