of late I have been getting tihis message whe trying to log into webmail :-
"Your connection is not secure
The owner of www.webmail.optusnet.com.au has configured their website improperly. To protect your information from being stolen, Firefox has not connected to this website." it says the certificate is not valid.
It might be just a problem with Firefox. Do you have another browser you can try and do you still get the same error from the link below?
Edit: Then again oziscot it might be an issue with the Optus website itself or the ssl cert as I had the same problem on Chrome tonight. Hopefully they will rectify the problem asap.
I think you are right and there is something wrong with the certifcate handling on the Optus webmail site. This came on suddenly. Your link works with no problems, however if I type the url directly into into Firefox or Chrome I get the error message. I have both browsers configured to warn me about unsafe websites.
Different browsers have different reactions to sites that are not secure but they are all attempting to do the same thing. When presented with a site with no security certificate most browsers will simply advise that the site is not secure. When presented with an input box or form many browsers will halt the action as you are now sending information over a website that is not secure as opposed to reading information.
From what I saw last night it appeared that something was incorrect with the security certificate or the way it was installed. Hopefully this error wont happen again.