John Carter responds to questions about Gmail. "Regarding the difference (as a user) between IMAP and POP for a Gmail incoming account, using an IMAP Gmail incoming account actually provides two benefits over a POP Gmail incoming account, but one of those benefits can appear to be an inconvenience and confusing if not clearly understood.

Let’s start with a simple display of what Mail looks like with an IMAP Gmail account:

Figure 1

With a POP Gmail account, the GMAIL mailbox you see above wouldn’t exist.

The arrows for Inbox, Sent, Trash, and Junk indicate that there are subaccounts. I have three subaccounts aside from Gmail, and the messages in those accounts are being collected by Gmail. If you have only one account, you won't see those arrows.

Figure 2 shows what an IMAP account provides that a POP account does not:

Figure 2

Everything you see in Figure 2 under [Gmail] are references to the actual mailboxes in the remote Gmail repository, and you can actually play around with the messages in those mailboxes as though they were local in your computer.

Let me expand those mailboxes under MAILBOXES in Figure 1 to show you:

Figure 3

“jrcarter” is my primary email. “AstroGimmicks” and “Sunrise Trust” are business accounts. The reality is that those three accounts actually forward their messages to the Gmail account. The Gmail account is a secondary personal account and is rarely given out and which has the primary purpose of delivering messages to Mail. And to be on the safe side, I have set up all four email accounts in Mail to collect messages. Complex, but that is my nature.

An IMAP Gmail account gives you access to all the mailboxes available in the remote Gmail mail repository as well as the local mailboxes (ON MY MAC). A POP Gmail account only gives you access to the local mailboxes. What gets confusing about the remote mailboxes is the “All Mail” mailbox, which is visible only by expanding both GMAIL and [Gmail] as shown in Figure 2.

TIP: In Gmail, they don’t call them mailboxes or folders. They call them labels. That’s rather confusing to anyone who ever used any mail program other than Gmail.

Any message that appears in the All Mail label actually resides in one of the other labels. If you delete a message from All Mail, it also gets deleted from the ‘real’ label. Deleting a message from any label other than Trash or All Mail moves it to Trash and it remains visible in All Mail (All Mail includes Trash). That’s another confusing aspect. The trick is to never delete anything from the All Mail label if you’re not sure which other label it actually resides in or if you don’t care if it gets deleted permanently. If you delete everything from the All Mail label, you delete everything from all other labels as well, including any messages you may have wanted to keep. Simply put, the All Mail label is only there to let you search for a message that might live in one of the other labels. Otherwise, leave it alone. To add even more confusion, sometimes I have deleted messages from All Mail only to see it show up there again. Stop chasing your tail and just manage messages in the other labels.

The really scary part is that if you delete a message from one label, it just might show up looking like a duplicate in All Mail and/or Trash. You can go crazy trying to track that down, so just worry about keeping Trash in the remote repository cleaned out regularly. And by the way, Trash in the local repository is not the same Trash in the remote repository.

I discovered that with an IMAP account, you can copy a mailbox from the local repository (ON MY MAC) to the remote repository (GMAIL) just by dragging it from within ON MY MAC to within GMAIL. That’s very useful, because if you created mailboxes in the local repository, you might prefer to see them in the remote repository when accessing mail from another computer or online. Just be sure to remove it from the local repository after copying it to the remote repository. Any Rules you had set up to move messages into a mailbox will NOT automatically update; you have to edit the rule to point to the new mailbox in GMAIL. Copying a mailbox with lots of messages may take time to trickle up, so don’t delete the local mailbox until you know it has completed the transfer.

This brings up the other major advantage of using an IMAP account over a POP account. If you keep all your mailboxes in the remote repository, you can access those messages from any computer anywhere by going online to access Gmail. Furthermore, if you have two or more computers that you access mail from (laptop and desktop), using IMAP on each computer gives you the advantage of accessing all your mail in any mailbox as long as those mailboxes are in the remote repository.

If what you have now is a POP Gmail account and you want to switch to an IMAP Gmail account, follow these steps:

Set the POP account to not include that account when checking for new mail (in the Advanced tab under Accounts).
Create the IMAP account (taking the defaults - don’t tinker yet).
This will retrieve ALL mail that was hanging around in the inbox of the remote repository.
Set the IMAP account to include that account when checking for new mail.
Copy the messages from the POP account mailboxes (Sent, Inbox, etc., but NOT from the ON MY MAC mailboxes) to the corresponding IMAP mailboxes, being careful not to duplicate any messages.
Disable the POP account (this makes it disappear from view, but does not delete it).
Now you can tinker with the preferences on the new IMAP account.
Copy any mailboxes from ON MY MAC to GMAIL that you want to access when accessing mail online or with another computer.
Delete the mailboxes from ON MY MAC that you copied to GMAIL.
Update any Rules that accessed a mailbox that has been moved.

Do we need a class on this?