Office 365 Update version 2604

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Office 365 Update version 2604

andy 5

Anybody else having issues with the latest Update blocking exchanges between Excel and Outlook using the Outlook.MailItem, have rolled back to 2603 and the VBA MAcro is working perfectly again.

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Answer 1

Jack Dang (WICLOUD CORPORATION) 17,340 Microsoft External Staff Moderator

Hi @andy ,

Thanks for reaching out.

For reference, the current 2604 release in the Current Channel is Version 2604 (Build 19929.20090), released April 21, 2026, and the published notes for it only list "Various fixes to functionality and performance" with no documented Outlook or automation changes. You can confirm this on the official update history page here: https://learn.microsoft.com/en-us/officeupdates/current-channel.

If you would like to send this directly to the product team, the most reliable way is from inside the affected app itself by going to Help > Feedback (or File > Feedback) in Excel or Outlook on the 2604 build, choosing I don't like something, and including the full build number, the exact VBA line that fails, and any error number or message shown. The official walkthrough is here for reference: https://support.microsoft.com/en-us/office/how-do-i-give-feedback-on-microsoft-office-2b102d44-b43f-4dd2-9ff4-23cf144cfb11. Submitting it from within the app is preferred because it automatically attaches diagnostic data that helps Microsoft trace the regression.

For now, I would treat rollback to 2603 as the correct workaround and wait for a newer Office build before testing again.

Hope this helps! If my explanation was helpful to your situation, I would greatly appreciate it if you could follow the instructions here so others with the same problem can benefit as well.

andy 5 Reputation points

2026-04-28T17:59:24.0466667+00:00
Ive rolled back and the problem is resolved.

Im using the following in Excel to email a specific worksheet to an individual. When run with the new software release it stops at the 'Send' reporting unable to use the email address or something like that (sorry cant be more precise or see the error as Ive rolled the update back)

Set OutApp = CreateObject("Outlook.Application")

Set OutMail = OutApp.CreateItem(olMailItem) With OutMail .To = EmailAddress(1) .CC = EmailAddress(2) .BCC = EmailAddress(3) .Subject = "xxxxxxxxx" .Body = Email_msg .Attachments.Add TempFilePath & TempFileName & FileExtStr .SendUsingAccount = OutApp.Session.Accounts.Item(3) .Send End With
Jack Dang (WICLOUD CORPORATION) 17,340 Reputation points Microsoft External Staff Moderator

2026-04-29T02:18:01.0366667+00:00

Hi @andy,

Thanks for your feedback.

If my answer was truly helpful to you, I would greatly appreciate it if you could follow the instructions here so others with the same problem can benefit as well.
Hornblower409 8,200 Reputation points

2026-04-29T23:56:20.3066667+00:00

@andy said

rolled back to 2603 and the VBA MAcro is working perfectly again.

Just FYI - This may be the same issue that is being worked in another thread:
https://learn.microsoft.com/en-us/answers/questions/5873845/recipient-add-problem-after-latest-updates

You might want to Follow that thread for any future updates from the other users or Microsoft.

Just to test a theory - Does the Outlook Profile you are using when you hit the problem have multiple Exchange email accounts?
Jack Dang (WICLOUD CORPORATION) 17,340 Reputation points Microsoft External Staff Moderator

2026-05-04T07:25:04.71+00:00

Hi @Hornblower409 ,

Thanks for sharing that thread. I agree this looks closely related.

From Andy’s sample code, this line is interesting:

.SendUsingAccount = OutApp.Session.Accounts.Item(3)

That suggests the Outlook profile has at least three accounts available in the profile, so your multiple-account theory is definitely worth checking. I cannot confirm from the code alone whether all of those are Exchange accounts, but it does point to a multi-account Outlook profile being involved.
Hornblower409 8,200 Reputation points

2026-05-04T11:49:22.6333333+00:00

@Jack Dang (WICLOUD CORPORATION) said

From Andy’s sample code, this line is interesting:
.SendUsingAccount = OutApp.Session.Accounts.Item(3)
That suggests the Outlook profile has at least three accounts available in the profile

Good catch. I missed that. Thank you.
andy 5 Reputation points

2026-05-04T16:56:57.94+00:00

hi @jack Dang , @hornblower409, yes you are correct I have a number of different exchange accounts in my Outlook and need to use a specific one to send the emials which is the '3rd' one in the list as they appear in Outlook. I have thought about creating a separate Profile with a single account as suggested by @hornbblower409, but have decided as Ive rolled the update back to 2603 and its working, ill leave it like this for the moment until I have a bit more time on my hands to experiment.. Thanks for your help.
Jack Dang (WICLOUD CORPORATION) 17,340 Reputation points Microsoft External Staff Moderator

2026-05-05T03:59:05.3566667+00:00

Hi @andy,

Thanks for your honest feedback.

If you found our explanations were truly helpful to you so far, I would greatly appreciate it if you could follow the instructions here so this thread can be closed. If you have new update in the future, feel free to post them on this platform and I'm happy to support. Thank you.

Answer 2

Yes, this aligns with a known pattern where recent Microsoft 365 Apps/Outlook builds break integrations and add-ins, and reverting to an earlier build restores functionality.

For VBA macros that use Outlook.MailItem from Excel, the behavior described is consistent with other recent Outlook/Office build regressions affecting add-ins and programmatic automation. In similar cases, the recommended mitigation has been to revert Office to a prior working build until Microsoft ships a fix.

For example, other Outlook/Exchange add‑in issues have been mitigated by reverting from a problematic 2603 build to an earlier 2602 build using Click‑to‑Run rollback commands such as:

"%programfiles%\Common Files\Microsoft Shared\ClickToRun\officec2rclient.exe" /update user updatetoversion=16.0.19725.20152

Since rolling back from 2604 to 2603 has already restored the VBA macro behavior, the practical options are:

Stay on 2603 (or another known-good build) and temporarily disable automatic updates for Microsoft 365 Apps until a newer build is confirmed to fix the issue.
Monitor Office/Outlook update release notes and known-issues pages, then re-enable updates and move to a later build once a fix is documented.

If the macro relies on Outlook automation from Excel (for example, creating or sending messages via Outlook.MailItem), no code changes are indicated in the provided material; the issue is with the Office build rather than the VBA pattern itself.

References:

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Office 365 Update version 2604

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