How do I resolve outlook emails stuck in outbox?

I am using MS outlook email account for the effective emailing communication. I have decided to use MS outlook email for various emailing purposes. MS outlook email has many unique and amazing features, so I select this email service for my official task. I am experiencing outlook emails stuck in outbox. This is a very common error experienced by many users. My email sending procedure takes a lot of time and message gets trapped in outbox. I don’t have skills to find out many reasons of this error.