I have three machines. A MacBook Pro, iMac 5K and an older iMac. All three run off the same email account. Emails come in to all three computers at once without issues and the ones that are irrelevant to each machine are binned as required. That is visible across the network - if one machine bins an email, it visibly disappears from the other Macs. However, I have now swapped the older iMac for an M1 Mac Mini. Upon starting it up for the first time, a load of emails that have already been read and deleted are sitting in the inbox and are all showing up as UNREAD. Also, new emails are now coming in that are being seen on all of the other Macs and iPhones but the Mini is not receiving any of them. So - previous, already read emails (about 100) in the inbox on first boot-up, all showing up as unread and new emails being received by all of our devices EXCEPT for the Mini. I'm not proficient at any of this so help is warmly received.