It probably is not causing your problem (as your husband uses Outlook) but the last release of Windows Live Mail was 2012 and Microsoft stopped supporting it in 2016 so you should really try to move off it.
Check your PlusNet mail settings to make sure you are using the correct ones. Check them here:
https://www.plus.net/help/email-guides/how-to-set-up-plusnet-email/
In the long term consider moving to a "web" based email system like gmail or Outlook.com as there is not "set up" required, you just logon to your email in your browser and all the emails are stored in "the cloud".
It also means you can logon to your email system on any computer in the world and do your emails, as well as on any smartphone or tablet, with no setup required.