I decided that I needed a break from the "never-ending" project on OMZs (oxygen minimum zones). So, I went to China for a four-week tour of four different labs/departments. After I left for China, the PI sent out the latest version of the manuscript for all co-authors to read. I was busy, and didn't check the email carefully.
Time went by, and I am back, to finish the paper. Somehow, I felt something was missing. So, I checked the PI's email, and discovered that one co-author was "dropped" from the mailing list. OMG!
I used to laugh at such email: "Please let me know if you do not receive this email." Well, I will not laugh again, but I will say: "Please reply to confirm you have received this email."