Is it possible to be automatically subscribed to all topics that I post in? It's a fairly common feature for Internet forums so I figure it would be a part of the phpBB this forum uses.

I know you can do that in SMF forums. But I'm not very familiar with phpBB forums. After reviewing my Control Panel, it looks like topics and forums can be subscribed to individually. And then they can be managed in Control Panel > Overview > Manage Subscriptions.

Notifications are handled separately (which is somewhat confusing). Control Panel > Board Preferences > Edit Notification Options.

Then I found one that either is exactly what you want, or else I have no idea what it does. But it sounds like it might be what you want. Control Panel > Board Preferences > Edit Posting Defaults > Notify me of replies by default. I don't know, but it might notify of every reply, rather than replies to your messages. But it probably can't hurt to try it. Just be close to your inbox, if you choose email notification, in case you start getting notified for every message posted.

Or maybe it would work better for you to use the Quick Links > Your Posts (right under the phpBB logo, top-left-ish area). When I tried it just now, it seems to show every topic that you've ever posted in. But it looks like it orders them by the topic which has the most recent reply (by anyone). It doesn't seem very helpful to me. But maybe it would work for you?