Microsoft has fixed an issue where replies to Outlook email would fail with the error message saying "Cannot send this item". This would typically happen when the email contained long links in the body. Microsoft has explained that it's Safe Links feature would lead to the exceeding of the 2084 Outlook URL limit as it adds additional characters to the URL.
On the support document describing the bug, Microsoft writes:
Outlook will display the error 'Cannot send this item' when the 2084th character in a link is an escaped character. This situation can occur with long URLs and when processed with Safe Links. When Safe Links wraps the URL it exceeds the 2084 Outlook limit for URLs and the URL gets truncated.
Other common symptoms with this issue include:
- URLs are truncated and when you click on them you may see a 404 Error.
- When you click on a link, Microsoft Defender may display an error message “The page that you are trying to access cannot be loaded” and “Due to an internal error, this web page could not be loaded. We recommend that you close this page.”
The issue has been fixed the issue by increasing the URL limit by nearly four times from 2084 to 8192. This was addressed with Outlook Desktop build 16116.10000:
This issue is fixed in Outlook Desktop build 16116.10000 and increases the URL limit from 2084 to 8192 characters. The Outlook Desktop fix is enabled at 100% of Current Channel as of April 4, 2023. Monthly Enterprise Channel will get the fix when it updates to Version 2302 (Build 16130.20218) and higher.
You can find the official support article here.
