I am aware of the issue of outlook receiving email but not sending. Been working on it much of the afternoon without a result so far so have escalated it to people who are smarter than me. If it is affecting you please open a support ticket from another account if you can, that way I can keep you informed with what is happening.
[UPDATE] This has been a tough one to crack. Some changes were made on the server.
In outlook go into the account settings and change the outgoing SMTP server port to 465 and be sure that SSL encryption is selected – how you do that differs in each version of outlook.
Any problems, open a support ticket at https://123host.com.au