Free Ones. Do The Paid Yahoo Email Accounts Drop Emails Like The Free Ones?

Do the paid Yahoo email accounts drop emails like the free ones? - free ones.

Lately I noticed that Yahoo sends fact that 15% of the messages I send. Let disappear in time, simply, even if they appear in my Sent folder. I noticed that many others have the same problem. I do not wish for something that does not, what do you pay for to pay. Can anyone tell me whether the payment service is more reliable than free?