The address book doesn't know the names. All it can see in an email message is the "display name" and it doesn't attempt to parse this into first name and last name as it has no way of telling how the display name is formulated. Analysing names is one of those things we humans consider trivial but teaching computers to do it is devilishly hard. If you were entering contacts into the address book by hand it would indeed construct a display name by concatenating first and last names as you typed them in. Next time, try using the email address crawler add-on. It can suck email addresses en masse out of your messages. https://freeshell.de/~kaosmos/index-en.html#eac You'd still have to manually fix the first and last names, but you won't have to do the whole importing thing 500 times. I would copy the display name, paste it into both first and last name boxes then delete the unwanted parts. Using ctrl+shift+left/right/home/end can select the unwanted part of the pasted name very efficiently. If your display names are well behaved, you might export your new address book to a CSV file, open that in a spreadsheet and use some cell formulae to split the display name into first and last, and insert those into the relevant columns. Save this enhanced version as a CSV file. Then you re-import this CSV file to generate a new address book. It comes down to whether the extra steps needed to automate the fix-up seem to be more effort than working through all the imported matter and editing it by hand.