Sending mail fails

After clicking send it ends up in Outbox Local accounts and is not sent.
Seems to involve only Microsoft accounts. Using online outlook.com has no problems.
I have updatet to the last version EmClient. Removed the account and added it again.
No solution.Familiar to anyone?

Hi, It is not just Microsoft Outlook, as it happens to me. and I don’t use Microsoft Outlook!!.
When I send an email it appears to stay in the outbox and throws up an Error box saying “failed to send etc”!! And at other times it sends an email without any apparent problem!! BUT, I have asked some people if they received an email from me after it has failed to go from the outbox to the sent folder and they have confirmed that they DID RECEIVE the email!!??
It is quite apparent to me that THIS ERROR THING HAS ONLY BEEN HAPPENING TO ME SINCE A RECENT EM CLIENT UPDATE!!!
It is time Em Client took notice of what their customers are saying and stop blaming somebody else!!
Jeff Turner.

Then it is a different issue. This topic is about sending through outlook.com.

As a test, can you completely disable any anti-virus, firewall, proxy or VPN, then try send again.
Sometimes even restarting your router may resolve this.

That is a server issue. The server has not confirmed the messages has been sent, so it is not removed from the Outbox.