You could add in your SWITCH ($Member.RecipientType)...
{($_ -eq "UserMailbox") -or ($_ -eq "Mailuser")} {
To include both cases of Onprem Mailboxes (Mailuser) vs O365 Mailboxes (UserMailbox)
Also you could add a default case for new cases that are not being handled.
You could add in your SWITCH ($Member.RecipientType)...
{($_ -eq "UserMailbox") -or ($_ -eq "Mailuser")} {
To include both cases of Onprem Mailboxes (Mailuser) vs O365 Mailboxes (UserMailbox)
Also you could add a default case for new cases that are not being handled.