Please don't laugh! :-) I may make a tit of myself even trying to describe my issue, here!
I am really non techy but my family, DH in particular, are hugely into tech and understand it all. My 'excuse' is that I'm almost 60.
DH and I have a very 'open' relationship when it comes to online, in that at a tiny click, he can see my emails, I can see his.
They're all gmail accounts. The thought behind it is that we have 'nothing to hide', I guess, though we've only talked about it once when a mate of mine who'd been emailing me was horrified to discover that, at that stage DH and I shared an email address! DH set up another just for me but anyone sitting here can log on and read any of my emails.
I have 'several' email addresses (which is a nuisance in itself); and use them for slightly different purposes. Some are no longer function which irritates me, but DH just 'moves on' to a new provider. Hence now gmail.
If you open our inbox, it'll open the default mailbox, but go top right hand corner, the 'account signed in' button, and that allows you to check any of the inboxes.
I want to email someone about slightly private business, and I just really don't want anyone else being able to casually open that mailbox, but -and here's the embarrassing thing- I have no idea how to set that inbox up so only I can open it! And I don't know how I would open it!
I will post (blurred) pictures if that helps.
And no, I can't ask DH to do it.