Good afternoon. After the upgrade, letters began to form groups and to disappear from the list of the previous day if they are received from the same sender to the next day. Can you fix it or make ability to disable this feature? 
Hello Denis,
This is enabled by a feature called ‘Conversations’ which groups together messages on the same subject. To disable it, please go to Menu -> View -> Conversations -> Disable conversations.
Regards,
Maurice