Outlook 365: Sending e:mails fail since 2nd week in March 2026

Question

'Sending an e:mail failure' in Outlook 365. This started a couple of days ago spontaneous, and exactly the same issue on 2 different PC's using the same Gmail account in Outlook !!

I followed many recommended steps, but no luck. New account created, Office 365 re-install etc etc.

I found out that Outlook 365 in NEW mode works just fine !!!! But lacks the Rules Wizard. Outlook 365 in CLASSIC mode continues to fail.

   Microsoft Outlook Version: 1.2026.303.100

   Client Version: 20260306001.08

Hope this helps in finding a resolution. I have not rolled back Outlook to a previous version. Any idea to fix this ? As I want the Classic Outlook 365, mainly for the Rules Wizard feature.

Answer 1

google mail is requiring oauth for imap logins. its been a rolling requirements, your account probably now requires it.

you may need to remove your current account and re-add it to get the oauth2 support.

note: as long as you left files on the server (imap), they should reappear when you add the account. if you downloaded emails to client, you need to save them first before removal.

Answer 2

Accept that the issue is acknowledged, but inform when a fix is available.

Answer 3

This issue has been widely reported, and Microsoft is currently working on a fix and plan to release the patch as soon as possible.

In the meantime, if you are experiencing this issue with Outlook Classic, try accessing your Gmail account using the web browser version of Outlook.

Also, until a patch is released for the Outlook Gmail account issue, please check out the solutions provided by Microsoft via this link.

https://support.microsoft.com/en-us/office/users-get-errors-0x800ccc0e-0x800ccc0f-synchronizing-gmail-and-yahoo-accounts-in-classic-outlook-e5a7b684-7c5c-4848-ab2d-d48291451f67

Answer 4

Classic Outlook for Windows has had several recent send/receive issues that were fixed by specific Office/Outlook updates. Given that:

• Sending fails only in Classic Outlook
• The same Gmail account works in New Outlook
• The issue started mid‑March 2026

the most relevant and supported action is to update Classic Outlook/Office to a build that includes the latest fixes.

Follow these steps on one of the affected PCs:

1. Open any Office app (Outlook Classic, Word, or Excel).
2. Select File → Office Account (or Account).
3. Under Office Updates, check the version.
4. If the version is older than the latest channel build, select Update Options → Update Now and let the update complete.

There are multiple known Outlook send/receive issues that are resolved only by updating to a newer build, for example:

• The metered-connection send/receive issue fixed in version 2008 (Build 13127.20508) or later.
• Other recent Outlook for Windows issues that are addressed in current builds listed in the update history.

If updating does not resolve the problem, use the automated troubleshooting tools for Outlook for Windows to diagnose and repair the profile and send/receive pipeline, as described in the “Resolve Outlook for Windows issues with automated troubleshooting tools” guidance.

As a fallback, if Classic Outlook still cannot send while New Outlook can, keep New Outlook for day‑to‑day sending and use Classic Outlook only for managing rules until a newer Classic build with a fix is installed.

---

References:

• Can't send or receive email in Outlook and "Metered Connection Warning" is triggered
• Fixes or workarounds for recent issues in classic Outlook for Windows
• I can't send or receive messages in Outlook