Two *.OST in outlook folder

Hello EveryOne,

My computer connecting to Domain and We use Outlook e mail client to connect to Exchange server.

I just wonder that,In the *.ost folder location C:\user\abc\App\Local\Microsoft\Outlook\

I saw two *.ost with "ABC@123.com.OST and ABC1@123.com.OST"

I tried to deleted ABC1@123.OST and leave ABC@123.com.OST and when i open Microsoft Outlook, it still created new ABC1@123.com.OST

Why Outlook not point to abc@123.com.ost that leaved in there?

and why it's created new abc1@123.com.ost??

Please let me know about this.

Best regards,