Osaka Post office
 

Where is the central post office in Osaka? Near Namba or Osaka/Umeda station? and it's open until 7 (9?)pm?

Otherwise, when does the post office at Kansai Airport open on Tuesday morning?

Last time I used it, which admittedly was years ago, the central post office was adjacent to Osaka station.

According to the KIX website, the post office is open from 9am-5pm every day except for some holidays.

Osaka Central Post Office is at:

3-2-4 Umeda, Kita-ku,
Osaka-shi, Osaka-fu,
530-0001

If the above address is not good enough for you then it is located right near JR Osaka station. Postal windows at Osaka Central Post office are open at:
Mon. – Sun. 7:00 a.m. – 12 midnight

Post Office at Kansai Airport is open at: Mon. – Sun. 9:00 a.m. – 5:00 p.m.

There will be US$ 5.00 or AUD 5.32 fee for this information which will be charged directly to your FlyerTalk account. :)

Looks like I'll have to ship stuff home today from the cental office then. The airport office opens later then I'd need it in the morning.

and I should stop buying things.

Note that the "postal windows" aren't the counters themselves but rather one window (perhaps two) in a separate section with extended hours (sometimes they're open 24 hours a day, but this post office isn't one of those).