Mac Mail - Pasting to BCC duplicates addresses
I send out a mailing list from my macbook pro, using Mail Version 11.5 (3445.9.1). I'm copying a list of email addresses from an Excel for Mac list and paste that into the BCC field of my mailing list. I perform this task approx 35+ times every week to different mailing lists.
I know this isn't the ideal way to be sending out mailing lists, however, it's just where I'm at right now. The real problem is that every time I paste the list into the BCC field, one email address gets copied into the BCC field multiple times. It can either be MY email address that I'm sending from OR one of the members of the lists....which means that member is getting added to multiple distribution lists that they do not belong to.
Does anyone have any suggestions on how to resolve this? Do I need to somehow clear my system cache after each time I send a distribution? Any suggestions would be greatly appreciated.
PLEASE NOTE: I tried to find the category for MAC MAIL to put this in the right topic, but couldn't find Mac Mail in any of the top categories.
MacBook Pro 13", macOS 10.13