IMAP or POP3? Setting Up Email Correctly in Outlook and on Mobile

One employee says an email they saw in Outlook yesterday isn’t on their phone today. Another’s laptop died, and years of work email went with it. In many of these cases, the cause is a simple choice made when the email account was added: POP3 instead of IMAP.

How does POP3 work?

With POP3, the email app downloads messages from the server and, by default, deletes them from the server right away or after a while. From then on, the email lives only on that computer; in Outlook, inside a local data file. The result:

• Messages don’t show up, or show up incompletely, on a second device such as a phone or webmail.
• Folders and sent emails exist only on that computer.
• If the disk fails, the laptop is stolen or ransomware strikes, the email is lost too, unless that file is backed up separately.

How is IMAP different?

With IMAP, messages and folders stay on the server, and each device is just a synchronized view of them. An email read or moved to a folder on a phone looks the same in Outlook and webmail. Sent emails are stored in the Sent folder on the server, and the mail server backup covers users’ email too. In a work environment where everyone has at least two devices, IMAP is the right choice.

The only cost of IMAP is that mailbox storage is used on the server, so each mailbox’s quota should match the user’s workload.

Server settings

Get the exact details from your mail server administrator, but the common pattern is:

• IMAP incoming: A server name such as mail.company.com, port 993 with SSL/TLS
• POP3 incoming (if needed): Port 995 with SSL/TLS
• SMTP outgoing: Port 465 with SSL/TLS or port 587 with STARTTLS, with authentication
• Username: Usually the full email address

Port 25 is for server-to-server communication and is not suitable for users’ email apps; many internet providers block it as well.

Setting up Outlook and mobile

1. In Outlook, choose to add an account and enter the email address.
2. If Outlook doesn’t detect the settings automatically, choose advanced or manual setup and select IMAP as the account type.
3. Enter the incoming and outgoing servers, ports and encryption type as listed above.
4. On a phone, in the built-in mail app or apps such as Gmail and Outlook, add the account as IMAP and enter the same details.
5. After setup, send a test email and confirm it appears in the Sent folder on every device.

Some business mail servers, including SmarterMail, can also sync calendars and contacts using protocols such as CalDAV, CardDAV or ActiveSync; exact features depend on the server version and license.

Converting a POP3 account to IMAP

Before removing a POP3 account from Outlook, make sure the old emails are on the computer and back up its data file. Emails that POP3 has deleted from the server will not come back when you add an IMAP account.

After adding the IMAP account, drag the old emails from the POP3 account’s folders into the IMAP account’s folders so they are uploaded to the server. If there is a lot of email, first make sure the mailbox quota on the server is large enough.

Checklist

• All users connect with IMAP, not POP3
• Incoming and outgoing connections use SSL/TLS encryption
• SMTP is set up with authentication on port 465 or 587
• The Sent folder is the same on every device
• Mailbox sizes match users’ needs

ITPlus724 engineers set up business email on SmarterMail servers and can also configure staff Outlook and phones and migrate old POP3 email for your company.