A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Thanks to all who responded to this!
Uploading the file that was giving us the problem was not an option due to the strict data security polocies within our company.
I do think that I solved it though. It seems that there were extra spaces between some of listed email addresses that were very hard to see due to the way that they were layed out in the cell. Making sure that each email address had a comma, and then only one space between it and the next email address seems to have resolved this.
Again, thanks to all who responded!