One of it was installed a week ago. It is called MS Outlook. Before it I used other email-clients. But I decided to change client. Only in a week of work, I noticed that some dozens of message disappeared from Inbox. I visited some articles over the Internet, someone suggested outlook pst repair tool, another person to forget about it, I don't know what to do pats.
You may transfer your data to MacBook on Outlook and to apply this...
Outlook Inbox Repair Tool (Scanpst.exe) is a utility that you can use in this case to repair your damaged archive.pst. It is highly recommended that you backup the damaged PST first as running the tool can irreparably damage the file.
1. Quit the application
2. Scanpst.exe is a hidden file so make sure that the 'Show hidden files and folders' setting is enabled in the folder options
3. Click Start | Search, or Find and type 'Scanpst.exe' in the Search box
4. Double-click to open the file and browse to the location of your damaged archive.pst
5. Click 'Start' to start the recovery process
6. Try to open the file in question again. The corruption problem should not exist.