Hello Tom Doyle,
Welcome to Microsoft Q&A forum.
I reviewed the Q&A Assist response on the thread. Its direction makes sense if you are using an Outlook app (for example, new Outlook or classic Outlook on Windows), because after a provider migration the account often needs to be re‑added using Yahoo’s current sign‑in and server configuration.
However, since this question is posted under Outlook Web (Outlook.com), there is one important point to be aware of: Microsoft removed the ability to add or sync third‑party accounts (such as Yahoo) as “connected accounts” in Outlook.com. In other words, Outlook.com itself may no longer be able to automatically pull new mail from a Yahoo-hosted mailbox. Reference: Connected email accounts like Gmail and Yahoo not working in Outlook.com
If your goal is to access the Cox/Yahoo mailbox and have it refresh normally, Microsoft’s documented options are to:
- Add the account in an Outlook app (desktop or mobile), or
- Use forwarding to an Outlook.com mailbox if you want to keep reading mail in Outlook.com.
For the Yahoo mailbox configuration itself, Yahoo supports both IMAP and POP, but IMAP is the typical “sync” option because it provides two‑way syncing (changes in the app reflect on the server). POP remains available but is more limited in how it retrieves mail. Yahoo also notes that third‑party clients may require an app password depending on the account’s security settings. Reference: https://help.yahoo.com/kb/SLN4075.html | https://help.yahoo.com/kb/SLN4724.html
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If you can share whether you’re trying to receive this mail in Outlook.com on the web or in an Outlook desktop/mobile app, the next step can be pointed in the correct direction without guessing.
I hope this helps clarify why the behavior changed after the migration.