Like GMail, Yahoo Mail has also started to provide HTTPS/SSL communication feature. You should enable this option for secure email communications. This can protect you against taping and several kind of Man-In-The-Middle attacks.
To enable HTTPS/SSL on your Yahoo Mail Account, go to "Mail Options" on your Yahoo Mail account and select "General" then check "Turn On SSL", and finally click to "Save:
To enable HTTPS/SSL on your Yahoo Mail Account, go to "Mail Options" on your Yahoo Mail account and select "General" then check "Turn On SSL", and finally click to "Save: