Problem with Outlook 10

Hi I wondered if anyone knew how to solve the problem of my outlook emails. I have been sending and receiving emails with no problems but now all of a sudden it will not send and they do not appear in the sent box either - This is from the main outlook when I click on the icon at the bottom of the screen.
If l go on the desktop mail box which is the shortcut version of my outlook email, l can send an email from there and view it in the send box.
I can also send and recieve emails normally if l log onto another computer.
I have only had the laptop since Febuaury and so it is all pretty new to me - have installed Office 365 and Kaspersky and made an outlook account as it was linked - seemed the easy option at the time.and everything has been fine until now - any advice would be greatly appreciated, thank you