OK have emailed Enta from another source, no reply yet. This email set-up was transferred from my old XP machine and has worked OK up to now, it occurred to me to try it out on my old machine, and it works! Mail can be sent out and received normally.
I am away for brief periods and use a 3 dongle on the offending machine, I have never been able to send out messages from Win Live when using the dongle but have learnt to live with it. All is well again once I return home and plug into Enta (except for now).
Have checked my settings which seem OK. Have tried to access my account through Webmail but am unable to do so, I could previously. Thank heaven I have other email facilities to fall back upon.