Multiple emails are usually outside of your control.
At each stage along the path that an email takes, the sending server transmits a message saying "Here's a message. Have you got it?". The receiving server then (hopefully) sends back a message saying "Yes, thanks. I've received the message".
If the receiving server doesn't send the 'thank you" message, the sending server resends the message and again waits for an acknowledgement.
Occasionally an email gets through without a problem but the 'thank you' message doesn't get received by the sending server. So a duplicate message is sent. If that doesn't result in a positive acknowledgement, a third copy is sent, etc, etc.
I've had problems where my email provider's server wasn't getting its 'thank you' messages out, resulting in up to 2000 copies of the same email ending up in my Inbox! So 2 copies shouldn't really concern you too much!
However, if the problem persists, you'll need to notify your email provider about the problem,so that they can look into it. (My own experience is that such problems usually only last a short while anyway).