Pro Tip: In your control panel, under “Track Delivery” you can see exactly what was received and what was sent on the various servers
Basics of email
There are only two possibilities with any email: It is either delivered or it is not delivered – nothing else. There is no mystery and no magic, only one of two possible things.
When you type an email and send it, your Internet connection opens a connection to your outgoing email server, your outgoing email server accepts your email and attempts to deliver it at the destination server.
The desitination server can either receive your email or reject it – there is nothing else.
If the destination email server accepts your email, further delivery to your recipient is out of your hands and it is up to the destination server to deliver the email (or lose / delete ) the email.
This process is the same for all people on the Internet.
So, if someone SENDS you an email, your incoming email server can either Receive it or Reject it – nothing else.
If someone says they have sent you an email and this email was delivered to your incoming email server, it will be in your email logs. If this email is not in your email logs, then the sender can check in their email logs, they will see that the sent email was never delivered to your server…
If someone says that they did not receive your email, but their server has accepted it from you, then their server has either lost or deleted your email.