For the last three weeks I have been getting an EMail authentication failure on one or more of my email addresses. If I do no nothing and let the email refresh on the next scheduled refresh the mail comes in OK, or if I do a manual check it comes in OK. It seems that if I just leave the automatic refresh on I get the failure. I ahve not had this problem before, I have changed nothing and I have had this account for nearly 6 years without problem. It happens on outlook and on my phone.
How often is your refresh cycle when left on automatic? Most mail providers restrict how often you can perform a manual sync (meaning, not push) in order to keep server load down. If you sync every 15 minutes, that should be fine. If you sync every minute on both devices, that can trigger a rate limit.
Just a thought.
I already thought of that and the email group is set to check every 30 mins. This has started happening in the last few weeks. I have not had an issue before and therefore have not changed any settings.