I use Microsoft Outlook to send emails. A lot of people you have a Yahoo address do not seem to get my emails......but they get emails from everyone else without issues. I am with Optusnet. So why is this happening? Is it a problem with Yahoo? Optus? some setting?
Email services like Yahoo and Hotmail have a Trusted Senders feature and sometimes they will block email until the sender's email address is added to that list. The email will not even go into the person's spam/junk folder, they just won't be delivered.