I got few messages from random people that they have been facing problems while using yahoo mail with outlook and i know how to fix this one, so here are some steps which you can take to resolve this issue:-
- Check your internet connection because sometimes it can cause this issue.
- Check your yahoo mail port settings
- Remove the Yahoo mail profile from outlook and then re-add it
- Check your Antivirus and Firewalls if it is not blocking you yahoo mail ports