4 Fixes ‘Error while preparing to send sharing message’ in Outlook

Some Microsoft Office users are encountering the “Error while preparing to send sharing message” error while trying to share their Calendar by sending an invite from within the application. This is reported to occur whenever the user tries to share any calendar, even the ones that are newly created. The error is typically encountered with, Outlook 2007, Outlook 2010 and Outlook 2016.

Error While Preparing to send Sharing Message
Error While Preparing to send Sharing Message

Note: Affected users report that sharing the Calendar through Office365 is successful as the recipient receives the calendar invitation through email.

What causes the Error While Preparing to Send Sharing Message

We investigated the issue and looked into various user reports to pinpoint the symptoms and determine the most likely causes. Here’s a list with potential culprits that might facilitate the apparition of the  “Error while preparing to send sharing message” issue:

  • Office file corruption – The error can occur because some Office files that are responsible for creating a bridge between Outlook and your Calendar app became corrupted and are preventing the process from completing.
  • An installed add-in is interfering with the sharing function – If you installed outdated or experimental add-ins for Outlook, one of them might be crashing the Calendar sharing function.
  • Permissions of the Calendar folder are damaged – This is an issue that is quite common on Windows 10. Most of the time, it occurs because an entry called PR_MEMBER_NAME is seen as a duplicate.

If you’re trying to resolve this particular issue, this article will provide you with a collection of effective troubleshooting steps. Continue down as we’ll feature a series of methods that have helped users in a similar situation to resolve the issue. For the best results, follow them in the order that they are presented. Let’s begin!

Method 1: Investigate & remove intrusive add-ins

Let’s start by making sure that the issue is not being created by one of the add-ins that you previously installed. A lot of users have reported that the issue was fixed as soon as they got rid of their installed add-ins.

Of course, if you’re using a lot of add-ins with your work, uninstalling each of them based on a hunch is less than ideal. Luckily, there’s a  way to verify whether an add-in is causing the “Error while preparing to send sharing message” error.  Follow the guide down below to verify if one of the add-ins is causing the issue and uninstall the one responsible for the issue:

  1. Press Windows key + R to open up a run dialog box. Then, type “outlook.exe /safe” and hit Enter to open Microsoft Outlook in Safe Mode. This command will open Outlook in Safe Mode, which will start the program with only the necessary components – add-ins and other enhancements will not be permitted to start.
    Run dialog: outlook.exe /safe
    Run dialog: outlook.exe /safe
  2. Wait until Outlook opens in Safe Mode, the try to send a calendar invite again from within the program. If the procedure is successful this time, it’s clear that one of the add-ins is causing the issue. In this case, continue down with the steps below. Otherwise, jump straight to Method 2.
  3. Close the Safe Mode version of Outlook and open the application again normally.
  4. In Microsoft Outlook, go to (using the ribbon at the top) and click on  Options.
  5. In the Outlook Options menu, click on Add-ins from the right pane. Then, go to the bottom of the screen, use the drop-down menu to select COM Add-ins and click the Go button.
  6. Start by removing the checkmarks of every available add-in. Then, systematically enable each of them one by one and while trying to send Calendar invites until you figure out which add-in is responsible.
  7. Once you manage to identify your culprit, select it from the COM Add-ins window and click the Remove button.
  8. Restart Outlook and the issue should stay resolved permanently.

If this method wasn’t applicable, continue down with the next method below.

Method 2: Reinstalling the Office suite

Some affected users have managed to get the issue resolved by reinstalling the Office suite. In most cases, this procedure is reported to be successful even if the Microsoft Office repair wizard was not able to get the issue resolved.

Here’s a quick guide on reinstalling the Office suite:

  1. Press Windows key + R to open up a Run dialog box. Next, type “appwiz.cpl” and hit Enter to open up Programs and Features.
    Run dialog: appwiz.cpl
    Run dialog: appwiz.cpl
  2. Inside the Programs and Features wizard, scroll down through the application list to locate Microsoft Office Entry.
  3. Right-click on it and click on Uninstall, then follow the on-screen prompts to uninstall the application suite from your system.
  4. Insert the Office installation media (or open the installation executable) and re-install the whole suite along with Microsoft Outlook.
  5. Reboot your machine and check whether the issue is resolved at the next startup.

If this method wasn’t able to resolve the error in your particular scenario, continue down with the next method below.

Method 3: Using the Calendar Permission button

Some affected users reported that they managed to find a workaround in using the Calendar Permission button to grant permissions directly. But keep in mind that this solution is merely a workaround and will not fix the functionality of the Share Calendar button.

The Calendar Permission button is located in the immediate vicinity of the Share Calendar button. To make use of this workaround, simply click on Calendar Permission and use the next menu to grant outside permissions to other users.

You can then click Add from the next menu to grant Calendar permission to other users. They should receive the invitation via email, just the same as if you were to use the Share Calendar button.

Method 4: Deleting all saved Outlook logins via Windows Credential Manager

A couple of users have reported that the issue was fixed after they used the Windows Credential Manager to delete all saved logins for Outlook and Exchange. This was reportedly successful in restoring the functionality of the Share Calendar button after the user reinserted their credentials in Outlook.

Here’s a quick guide on using the Windows Credential Manager to delete all Outlook & Exchange saved logins:

  1. Press Windows key + R to open up a Run dialog box. Next, type or paste “control /name Microsoft.CredentialManager” to open up the Credential Manager  Windows application.
    Run dialog: control /name Microsoft.CredentialManager
    Run dialog: control /name Microsoft.CredentialManager
  2. Under Manage your credentials, click on Windows Credentials.
  3. Scroll down to Generic Credentials and remove every entry that mentions Office, Outlook or Exchange. You can do so by expanding the drop-down menu associated with each entry and choosing Remove.
    Expand Credential Manager's entry drop-down menu and click on Remove
    Expand Credential Manager’s entry drop-down menu and click on Remove
  4. Once every associated entry has been removed, close Credential Manager and restart your machine.
  5. At the next startup, open Outlook and reinsert your log-in credentials. You should be able to share your Calendar without issues after you log back in.

Kevin Arrows

Kevin Arrows is a highly experienced and knowledgeable technology specialist with over a decade of industry experience. He holds a Microsoft Certified Technology Specialist (MCTS) certification and has a deep passion for staying up-to-date on the latest tech developments. Kevin has written extensively on a wide range of tech-related topics, showcasing his expertise and knowledge in areas such as software development, cybersecurity, and cloud computing. His contributions to the tech field have been widely recognized and respected by his peers, and he is highly regarded for his ability to explain complex technical concepts in a clear and concise manner.