As the other answers already suggest, the Pi is pretty much capable to serve these needs. It also also likely to survive its time (see also here). To add to the list of references: I have a remote data logging running 24/7 for almost two years now on a type B. The system's current uptime is 183 days, which is not even the Pi's fault.
However if you setup a mail server you might want to consider to not keep your mailbox solely on the SD-card but implement a backup scheme to regularly mirror it to another storage device. Rumor has it that power brown-outs may ruin SD cards on the Pi.
Same goes for the chatlogs if you have an inclination to hold on to these.