duplicate emails

Question

duplicate emails

Ralph Pulido 0

I am receiving duplicate emails on mac new outlook pop account? How do I fix?

John Jefferson Doyon 88,075 Reputation points Independent Advisor

2026-04-15T20:03:09.9966667+00:00
Hi, I'm John! I will help you with this.

To help narrow down the issue:

Are you using POP or IMAP for this account in Outlook for Mac?

Did this start after switching to the “New Outlook” version?

Do you also have the same email added on another device or app (phone, another PC, etc.)?

A common cause with POP accounts is that messages are set to stay on the server. This can make Outlook download the same emails multiple times.

1 answer

Your answer

John Jefferson Doyon 88,075 Reputation points Independent Advisor

2026-04-15T20:03:09.9966667+00:00

Hi, I'm John! I will help you with this.

To help narrow down the issue:

Are you using POP or IMAP for this account in Outlook for Mac?

Did this start after switching to the “New Outlook” version?

Do you also have the same email added on another device or app (phone, another PC, etc.)?

A common cause with POP accounts is that messages are set to stay on the server. This can make Outlook download the same emails multiple times.

Answer 1

Duplicate messages with POP are usually caused by the mail server delivering the same items repeatedly, or Outlook not tracking which POP messages were already downloaded.

In an Exchange Server 2010 POP3 scenario, this can happen when Outlook is configured to “Leave a copy of messages on the server.” Because of a server-side issue, Outlook cannot correctly determine which POP3 messages were already downloaded, so it downloads all messages again every time it starts, creating duplicates.

The documented fix for that specific scenario is:

Ensure the Exchange Server 2010 environment has Update Rollup 4 for Exchange Server 2010 Service Pack 1 (KB2579150) installed on the Client Access Server role.
After the update, Outlook will be able to correctly track which POP3 messages have already been downloaded, so duplicates stop appearing.

If the POP account is hosted on an Exchange Server 2010 environment and duplicates started after enabling “Leave a copy of messages on the server,” contact the mail/Exchange administrator to verify that this update rollup is installed on the server.

References:

Outlook downloads duplicated POP3 email messages in an Exchange Server 2010 environment