IMAP, POP3, and ActiveSync

Three paths, three results

The same mailbox can be opened three ways. IMAP leaves the mail on the server. A message read or deleted on one device changes on the other device too. POP3, on most setups, downloads the mail to one computer. The copy on the server can be deleted, depending on the client setting. ActiveSync also syncs contacts and the calendar, not only mail. The OwnHost corporate mail page names all three. The FAQ says sync happens with IMAP or ActiveSync. Do not set up POP3 as “the mailbox that stays the same on every device”.

The corporate mail card lists Exchange ActiveSync. That line is not a Microsoft Exchange server. The corporate mail hosting introduction says so. The local email card has no ActiveSync. It lists POP and IMAP. If contacts and the calendar must sync, look at the ActiveSync line on the corporate card. If mail alone is enough, both pages open with IMAP.

IMAP

IMAP keeps folders on the server. Inbox, sent, drafts, and folders you create also show on the phone. New mail lands in the mailbox while the client is closed. When the client opens, the list refreshes. More than one person can open the same address with IMAP. If one deletes, the other sees it deleted too. Do not call that a shared-mailbox license. It is sharing the same password. A separate permission is not written on the page.

The quota is on the server. IMAP does not escape a full mailbox onto the computer’s disk. Corporate Mail 10 gives 10 mailboxes 100 GB in total. Because the message stays on the server, that pool fills up. Seeing “downloaded” on the phone does not mean the server copy was deleted.

POP3

POP3 is written to empty a mailbox into one client. Many programs, by default, delete the message from the server after download. A second phone does not see that message. If “leave a copy on the server” is checked, the message can stay for a while. That setting is not in the same place in every program. If the check is forgotten, the archive is on one computer. If that disk fails, there may be no copy on the server to bring back.

POP3 does not carry a calendar or contacts. It is mail only. When you set up a new laptop, the old POP archive is not on that laptop. The file has to be moved by hand. For a mailbox used on more than one device, IMAP leaves fewer surprises.

ActiveSync

ActiveSync syncs the address book and the calendar together with the mail. When a meeting changes on the phone, the calendar on the server changes too. The corporate card writes this line. The local card does not. ActiveSync does not open an Exchange admin panel. A shared room mailbox, a retention policy, or an Outlook add-in is not written on the page as part of this line. Webmail separately names a shared calendar, tasks, and a global address book. Those are on the MailEnable or SmarterMail screen in the browser. They are not the same button as ActiveSync on the phone.

Read the server name from the panel during setup. This article does not ask you to memorize a server name. The username is the full address: name@yourcompany.com. The password is the mailbox password. Choosing Exchange as the account type does not mean an Exchange server is there. Many phones label an ActiveSync account as Exchange. The label does not rename the product.

Webmail

Webmail is the mailbox opened in a browser. It installs no program. Forwarding, an auto-reply, groups, and the quota are on that screen. If the phone is lost, webmail still works. Changing the password there also drops IMAP and ActiveSync sessions. Do not leave the account open on the old phone.

Sending is about 500 messages an hour. Webmail counts toward that limit too. An auto-reply that answers every incoming message can fill the limit. Do not tie a vacation note to a public list. Bulk mail is forbidden. The detail is in the plans article.

Which one to set up

If the phone and the computer should see the same mailbox: IMAP. If contacts and the calendar should sync too, and the card is corporate mail: ActiveSync. If mail will live only on one office computer and you do not want a server copy: POP3. On that choice, take a backup separately. The server copy can disappear. If the local card has no ActiveSync, continue with IMAP. If the calendar need means moving to the corporate card, the move is in the migration article. Where the mailbox sits is in the local email article.

After setup, delete the same message from two devices. If it disappears on the other one, IMAP or ActiveSync is working. If it does not, POP3 has downloaded a copy. See that difference on the first day. Do not go looking a month later for which disk holds the archive.