I work for a magazine with a substantial mailing list, and it has recently come to light that a large number of our would-be contacts have been omitted from our contact submissions. We are hoping to rectify this in the near future by re-uploading our entire contact list.
I am expecting the majority of the list to be duplicates and to merely be updated (or discarded in the case of previous unsubscribes), but I was wondering if there is anything I should do to reduce the risk of duplicate entries or if there are other issues I should be on the lookout for.
Thanks!