I have two Yahoo mail accounts setup on my Mail app on my Lumia 925. My phone is about a month old now, and I have intermittent problems with my Yahoo mail accounts. Once in a while, when I open the Mail app, it prompts me to enter one of my two Yahoo mail account passwords. This has happened more than a dozen times already since I got my phone, and usually prompting just for one of my accounts. I also have two Gmail accounts setup on the same Mail app and I have never been prompted for my passwords for those accounts.
What can I do to prevent this from happening again?
EDIT
A factory reset did not help at all, with one of my Yahoo accounts asking for my password within the same day.