Unable to send Email with Attachments

Just recently set up eM Client and I thought all was well.  I was really happy with the layout and workings of the program until just yesterday. I tried to send an email with an attachment (1.2MB) and it wouldn’t leave the Outbox. 

I contacted email Host copying them the error message and they suggested trying two alternative Port numbers but that changed nothing.  I have been using Windows Live Mail and I had to go back to that in order to send my email. My email Hosts are saying at this stage that it must be a problem with my email client.

Is there anyone can through any light on this problem please?  Don’t really want to ditch eM Client but if there are no solutions then it’ll have to be.

13:27:06 XXXXXXXXXXXX A/C[SMTP]  MailClient.Accounts.SocketException: Sending messages failed due to the following reason: 
13:27:06     “Unable to read data from the transport connection: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.”
13:27:06    at MailClient.Protocols.Smtp.SmtpSendCommand.Execute(WorkerStatus status)
13:27:06    at MailClient.Commands.Command.Process(WorkerStatus status)