MC1293480 - Exchange Online: Retirement of legacy TLS versions for POP and IMAP connections

Introduction

We are retiring support for legacy Transport Layer Security (TLS) versions for POP3 and IMAP4 connections to Exchange Online. This change improves security and aligns with current industry standards. TLS 1.0 and TLS 1.1 are no longer considered secure. Most modern email clients already use TLS 1.2 or later. 

When this will happen

• Rollout start: July 1, 2026
• Rollout end: December 31, 2026

The rollout will occur gradually worldwide.

How this affects your organization

Who is affected

• Microsoft 365 tenants using POP3 or IMAP4 with Exchange Online
• Admins managing email clients, applications, or devices that use POP or IMAP

What will happen

• POP3 and IMAP4 connections will require TLS 1.2 or later.
• Connections using TLS 1.0 or TLS 1.1 will fail.
• Modern email clients are not expected to be affected.
• Legacy applications or devices may stop connecting.
• Custom or embedded systems may require updates.

What you can do to prepare

• If you use POP or IMAP with Exchange Online, ensure email clients, applications, and libraries support TLS 1.2 or later and do not use legacy TLS endpoints.
• Review all POP and IMAP clients in your organization.
• Confirm support for TLS 1.2 or later.
• Update or replace clients that rely on legacy TLS.
• Validate TLS support with third‑party vendors.
• Inform helpdesk and operations teams.

No action is required if all connections already use TLS 1.2 or later.

Compliance considerations

No compliance considerations identified. Review as appropriate for your organization.