[ms office - 2016] Outlook - default send from using multiple mailboxes

[HereIGoAgain2601]

Hello

 

We have a number of users who have access to multiple mailboxes. We do this by granting their individual user account Full Control of the mailbox in O365. It then shows up as a secondary mailbox.

 

We have had a complaint this week that when opening the secondary mailbox, and attempting to compose a new message, the "From" address is still set to the user's default O365 personal login. I'm not sure if I am remembering incorrectly, but i seem to recall that when we used to click between the mailboxes the "from" would update to the currently acitve account. Am I mistaken?

 

Just wondering how everyone else has experienced this as the user is quite insistent that they never used to have to manually select the correct address before. To make things worse it's the headteacher!

 

Thanks