Set up 5 email accounts when I signed up for basic bundle back in 2007. If I now cancel this service ( no longer need landline and ADSL is being turned off ) and rely on my mobiles only what will happen to my email accounts?
You must have a landline internet plan to have email addresses (One of the main reasons they're offered is to make it hard to leave as you lose them). FWIW migration ahead of time is now pretty easy.
Just setup a free gmail account (or 5 if you still want to keep five external addresses).
Gmail can import all existing posts from Optus easily
Then set GMail to grab any new emails (it can be set to colour tag emails coming from external servers).
Next update all the majors (Banks, 2FA, Utilites, etc.) with the new email addresses.
Email your contacts with the new address
Watch as less and less emails arrive via Optus.
Finally pull the pin.
Oh and do set up 2 factor authentication. You'll find spam handling is also much improved.
Actually 60 days it is according to another post by a moderator. If you purchase a $15 data sim plan I believe that's all you need to retain your email or you can go with what Peter said.