Why doesn't Apple mail download Gmail messages that were sent to myself?

Question

When I e-mail myself to my Gmail address, the message sits in the Gmail inbox but Apple
Mail doesn't download it.
Mail downloads every other message in the Gmail inbox, but not the ones i've addressed to myself to my Gmail address.
Any ideas for why this is happening?

Answer 1

Gmail POP access doesn’t work like a normal POP mail server would. Here are some of its idiosyncrasies:
1. Messages downloaded by any conventional POP mail client are marked as downloaded at the server (but not as read on the web), and no longer available to either the same or any other POP mail client.
2. To make already downloaded messages available for POP access again, you must go to Gmail’s Settings > Forwarding and POP page, select Enable POP for all mail, and click Save Changes, which causes everything (and I mean everything) still on the server to be downloaded again.
3. The Mail > Preferences > Accounts > Advanced > Remove copy from server settings have absolutely no effect on the messages stored on Gmail’s server. Gmail ignores any requests to delete messages from the server made by a POP client. What happens to the messages on the server after a POP client has downloaded them is determined by Gmail’s Settings > Forwarding and POP > When messages are accessed with POP setting alone. In the case of Gmail (and only in that case), I recommend turning OFF Remove copy from server in Mail, so that Mail doesn’t even try to remove any messages from the server, regardless of whether you do actually want already downloaded messages to be removed from the server after some time or not.
4. Messages sent using the web interface will be downloaded by your POP mail client as if they were received messages. Although this may seem weird, it's good because it allows archiving all messages locally in Mail, regardless of how they were sent — as long as you don't access the same Gmail account with more than one POP mail client, that is. You can set up a rule in Mail to automatically route those messages to the appropriate Sent mailbox (or to any other mailbox for that matter) if that's what you want.
5. Messages sent using a POP/SMTP mail client such as Mail are also treated as if they were incoming messages for POP purposes, just as in #4. What prevents them from being downloaded is that Gmail marks them as already downloaded immediately. Since they’re on the server nonetheless, already sent messages would be downloaded together with all the other messages on the server if proceeding as described in #2.
6. A particular case of #5 are messages sent to yourself. Instead of putting a copy of the sent message in the server’s Inbox and making it available for download, both the sent and the “received” message on the server are actually one and the same, and hence, cannot be downloaded via POP for the reason explained in #5.
7. Gmail allows POP accounts to be set up in a special way that avoids some of these issues while introducing others. If you only need POP access to the last 30 days of mail, you may configure Mail in “recent mode”, as described in Using POP on multiple clients or mobile devices. Configuring the account this way would allow Mail to download messages marked by Gmail as already downloaded (and download messages sent to yourself in particular), but it would also cause all sent messages (not just messages sent to yourself or through webmail) to be downloaded as if they were received messages.