If you still exchange contacts and calendar items between Microsoft 365 and Salesforce using Lightning Sync, you have missed a deadline. Salesforce advised completing the Lightning Sync to Einstein Activity Capture migration before August 2026, precisely to keep syncing from stopping without warning. That month has passed. It is not a disaster, but it does turn the migration into catch-up work with a hard date behind it.

Two dates you need to keep apart

There are two clocks running here, set by two different vendors.

  • Microsoft. Exchange Web Services (EWS) is being retired in Exchange Online. Microsoft starts disabling EWS globally for all organisations from October 2026, with full disablement scheduled for April 2027. This applies only to Microsoft 365 and Exchange Online; nothing changes for EWS in on-premises Exchange Server.
  • Salesforce. Lightning Sync itself retires in April 2027.

The date that binds you is almost always the first one. A Lightning Sync configuration that authenticates over EWS stops syncing the moment EWS is switched off in your tenant, which can happen as early as October 2026. Waiting until April 2027 because that is when Lightning Sync disappears means months of silent outage in practice.

How to check whether this affects you

Three checks, in this order:

  1. Confirm you still use Lightning Sync. In Setup, open the Lightning Sync configuration and look at which configurations are active and how many users are assigned to them. If a configuration has no users left, this is the moment to remove it rather than migrate it.
  2. Establish the connection method. If the connection runs over Exchange Web Services, the Microsoft date applies to you. If it runs over Microsoft Graph or over Google, the EWS retirement does not affect you, but the Lightning Sync retirement in April 2027 still does.
  3. Check the Microsoft side too. The Microsoft 365 admin center offers EWS Usage Reports showing what traffic still runs over EWS. That is where you find out whether applications other than Salesforce are leaning on EWS as well, because they have the same problem.

The migration is two steps, and the order matters

Salesforce describes it as one project, but it is two, and you do not get to pick the sequence.

First you migrate from Lightning Sync to Einstein Activity Capture. There is a Lightning Sync migration tool for this: you grant users the Einstein Activity Capture permissions and then turn Lightning Sync off. Only once that is done do you upgrade the authentication from EWS to Microsoft Graph. Starting at the other end only creates extra work.

Einstein Activity Capture is not the same feature under a new name. Alongside contacts and calendar items it also syncs email, gives you more control over what happens to that data, and is the foundation the AI and agent features in Salesforce build on. That also means you get to make the choices about data storage and visibility again. So work through the Salesforce considerations page before you switch the tool on, not after.

Treat it as a project, not a checkbox

This migration touches the calendars and mailboxes of your entire sales team. That does not make it technically heavy, but it does make it sensitive: if syncing stops for a week, everyone notices and nobody reports it. Plan it with a pilot group, a verification moment, and a clear date on which Lightning Sync goes off.

Not sure which connections in your org still lean on EWS, or would you rather have the migration guided? Our consultancy walks through your org and records what needs doing, in what order. While you are looking at integrations, our piece on the Salesforce API and custom integrations is worth a read.

Get in touch if you want this settled before the Microsoft date.