Outlook email

It is safe to remove the old email account from classic Outlook, but first preserve any mail, contacts, or calendar items you may need and identify whether its files are .pst personal data or .ost cached data.

1. Identify the old account’s files

In classic Outlook:

1. Select File > Account Settings > Account Settings.
2. Open the Data Files tab.
3. Note the file name, location, and associated account for every .pst and .ost file.^1^
4. Do not delete the entire Outlook Files or Microsoft\Outlook folder—other accounts or archives may use files there.

The file type matters:

• .pst — may contain irreplaceable local mail, contacts, calendars, or archives. With a POP account, all this information is stored in the .pst; Windows 10 and 11 commonly place it under Documents\Outlook Files.^2^
• .ost — normally an offline cache of a server mailbox. Do not delete it unless the required information still exists on the mail server or has been exported first.

2. Back up anything you want to keep

If you may need old messages, contacts, or calendar entries:

1. Select File > Open & Export > Import/Export.
2. Choose Export to a file > Outlook Data File (.pst).
3. Select the old mailbox and include its subfolders.
4. Save the backup somewhere outside the Outlook data-file folder, such as an external drive.^3^

Keep that .pst until you have opened it and confirmed that the required information is present. To test it, use File > Open & Export > Open Outlook Data File.^4^

3. Remove the old account

After the backup:

1. Select File > Account Settings > Account Settings.
2. Select the old Comcast or other unused account.
3. Select Remove, then Yes.

Removing it from Outlook stops Outlook from sending and receiving through that account; it does not cancel or deactivate the email address with the provider. Outlook warns that offline cached content for the account will be removed from the computer.^5^

If this is Outlook’s last or only configured account, Outlook may require a new data location before allowing removal.^5^

4. Clean up files afterward

Close Outlook before deleting anything.

• A .pst should be retained if it contains old messages, contacts, calendars, or archives you want. Deleting it permanently deletes that local copy.
• An old .ost can be removed only after confirming it belongs to the removed account and that no unique local information is needed.
• Other files in the Outlook folders may belong to active accounts, profiles, or archives, so deleting the complete folder is not recommended.

Your new Yahoo Mail can remain browser-only; it does not have to be added to Outlook. If it is not configured in Outlook, removing the old account will not affect the Yahoo mailbox.

References

1. Repair Outlook Data Files (.pst and .ost) | Microsoft Support
2. Find and transfer Outlook data files from one computer to another | Microsoft Support
3. Back up your Outlook email | Microsoft Support
4. [Classic Outlook](https://support.microsoft.com/outlook/open-and-close-outlook-data-files-pst)
5. Remove or delete an email account from classic Outlook for Windows | Microsoft Support