You should be able to export both the e-mail folders from Outlook 2010 (perhaps you have already done so) and the same for the address book. Backup all of that first! I suspect that the two versions are trying to take use the same or similar area to store e-mails and such and things are getting complicated in that area. You can move the location of the data folders in Outlook and if you're trying to keep the two versions separate, make sure to set the path for the 2016 version to a different folder.
But the easiest solution would be to switch to something that works a bit better for you. I can second the recommendation for Thunderbird, although you need to keep in mind that moving e-mails and such from Outlook to Thunderbird can be challenging. Read up on that first. OTOH, if the e-mail account is set up as IMAP, you should be able to use any client and just add the account. Everything should be there. If it is set up as a POP3 account, back up everything before you lose stuff!
As has been mentioned, Outlook has its quirks (I'm staying civilised) and using a 13 year old version doesn't help. Even the 2016 version is still getting a bit long in the tooth by now. The newer versions won't look all that different, you could also consider investing in a newer licence, but Thunderbird is a lot cheaper!