As suggested, I would also encourage you to use separate emails for each of you, no matter how close you are— and that's coming from an almost 30 years (and counting) lasting couple.

To be clear, we both have full access to the other accounts (email, health, everything, including financials) so keeping our own little 'secret' is not what's at stake for us (not mentioning that we simply respect the other's privacy). We just want to remove useless noise from our inboxes, and to be honest I really don't care much about reading her emails like she doesn't care about reading mine much either ;)

So, we own both our own domain name (name/surname). I also own other ones, including the one I'm using to log in here and to blog. I also heavily rely on email aliases/relays to subscribe to whatever I want to, so I know can always easily delete a spam-contaminated alias the moment I notice it starts sending me too much spam, without compromising my main email.