I received this "MAPI error 0X80040107 was reported" after I attempted to import a .csv file

Just based on the info provided

#1 - Sounds like you have invalid contact items which can be the result of a problematic sync - but for sake of discussion, let's not focus on the "cause" of the invalid contact items but rather purely that invalid contact items exist "however caused" - reason for that initial assessment is the error encountered which is "0x80040107 = Invalid_EntryID" couple with next item

#2 - "Do not import duplicates" requires that existing contact items be dchecked against incoming imported items which definitely explains why existing contact items are being accessed. That's something that is not an issue when the "allow duplictes" option is selected. This is not a suggestion that this is the correct option to select but merely to state potential cause and effect of what was chosen

#3 - The fact that some contact items have imported assists in narrowing down which contact items have a potnetial issue. Go through the input data file - the items imported should be sequential. Find the first item after the last successfully imported contact and you have your starting point of what to be looking for. Since this is an Exchange account - you will need your Exchange admin to assist in fixing the contact folder.

Don't understand email addresses showing up in 2 row/cells other than there will be garbage records. Also, if whatever process you used to delete duplicates didn't change the "named range" in the worksheet - your also going to have garbage or blank records in your worksheet.