duplicate emails

After someone responds to an e-mail I had originally sent to them, I in turn respond to that e-mail they had sent to me. Outlook 365 sends out the response I wrote, along with another e-mail, but that one is always blank. How can I stop this from happening?

Hi, I am running Outlook 2010 32-bit and I have a single PST for multiple POP3 email accounts (it works best for me to have all incoming emails in a single inbox and all emails i send into a single 'sent' folder). But many times, people send emails to more than one of my email accounts...

Been using Outlook 2010 for ages, admit that my inboxes on both the server and in outlook profile contain many emails. I need to keep emails still on the server. Starting yesterday , with no update from outlook software since June 2017, my inbox started downloading all the emails on the...