Exchange Online - Seeing all aliases of dist list

Hello all,

We are preparing to sync our on prem AD distro groups and mail enabled security groups to O365, with a migration of email to EO to follow.    (We already have user accounts synced via Azure AD Connect.)

One gotcha, is that we have old email addresses (with unused domains) on these groups and I'm not sure if thats going to be a problem if I sync then before stripping those out.   I was able to script removing those from the user accounts before we synced those, though doing it for the groups hasn't been successful so far.

I went ahead and synced a couple of DG's to O365 just as a trial run, and when I view the groups in Exchange Admin Center / Groups/ Dist List, it shows the primary email email address and two of the alias addresses.   Then it shows '+3 more'.   I can't figure out how to view those '3 more' aliases.   I'm wanting to see if those additional addresses are good addresses (with our domains that do exist in O365).   If so, then I would seem that the sync leaves out the 'bad' addresses, if that makes sense.

Thanks for any pointers!