I've had a yahoo mail account for over 10 years now (and my wife has as well). For me it's a marginal account which I don't use that much (I keep it for family members to contact me who just can't get the idea of changing) but for her it's been a primary account which she's loved for many years (in terms of domain recognition). Their reliability has always been good in my opinion over these years, the problem is the quality of their web client which seems to have hardly moved on at all since I originally opened the accounts in 2005. My wife pulls her mail over iOS primarily so she doesn't notice, but I've always been surprised that they've never spent more time on this core service. Maybe that's a reflection of why they are where they are now though.....
Yandex mail was also down for a short while today in Europe. We might be watching a moving DDoS in progress.