List import - How to not overwrite a particular existing record field

[Nurture_Ninja]

I'm doing a list import from an event booth visits. I have about 100 leads to import and some of these already exist in our db. 

I want to import the new 70 leads and also update the existing 30 days. Only field I don't want to update the 'Job title' for the existing 30 leads. Here, I want to retain the value in our db. Is it possible to achieve this? Thanks.

[SanfordWhiteman · Accepted solution]

Go into Admin » Field Management and Block Field Updates for that field from source List Import/List Import (untrusted).

You can make this change temporarily and then change it back when the import is complete, if it’s not something you always want to block.

[Nurture_Ninja]

Thank you. Can you please explain why does it need to be List Import untrusted source and not List Import trusted source? 

[SanfordWhiteman]

I meant you could use either one, depending on how you’re doing the import.