Do you see Operation could not be performed when you try to send emails?
Here are the reasons and solutions when you see this error message operation couldn’t be performed when trying to send emails. There are many other incidents to see these operation-related messages like enable a flag for emails, move the emails to some specific folders, etc.
The above tasks clearly state that the user tries an operation on the outlook mail application and it encounters and ends up with a message stating that the operation could not be performed.

Few Solutions for Outlook operation not performed related issue:
This error message occurs due to the changes in the outlook mail configuration. Check the email settings like POP or SMTP and test email send / receive process.
Repair the program from the control panel.
Restart the computer to verify if the issue is temporary and is fixed.
If you are facing this error message in some regular time intervals, then we have to clear the temporary files from outlook and need to reset the settings, and create new outlook mail profiles to verify the issue.
Check for office updates and install them.
Check Windows updates as well and install them.
Manage the other user-profiles and see if the other users face the same issues.
Outlook mail app is used by the home and business users and company people for daily email works including calendar, tasks scheduler, and reminders. Address book to store all the contact-related information.
This operation could not be performed may affect contacts, calendar as well. This requires the user to solve the email-related issues or contact the email support team for help. It gets started usually when some incompatible programs are loaded and removed from the computer.
The malware issues or some temporary files, abrupt system restart, the improper shutdown may leave you to get this kind of error message. For more help, contact chat support here on this operation issues page.
Related Error codes:
Something went wrong error code
Background installation support