It seems that my problems with Telstra's new email system has, as of 21 March, (as far as I can tell) been resolved.
On 21 March my inbox was flooded, I even received an email from an emailed circular I hadn't seen for 8 months !
It's very easy to sit back and criticise Telstra but as I live in a regional area, the only viable alternative is Optus which has a worse track record than Telstra.
So I'm very pleased to say I am now receiving the service I pay for and hopefully, this situation will be maintained.
Thank you Telstra tech Help, it is much appreciated.