Every now and again I get this error when sending emails "server error 550 5.7 1 relaying denied proper authentication required...". The emails do not go. No problem receiving emails. Using Outlook 2019 desktop client. My account settings have been the same since always - "No encrypted connection; and no logon using secure password authentication". Have changed password a couple of times.. The only way to rectify the problem is to reset the modem. Turning off and restarting the modem doesnt do it.