double messages received, although only one message was sent

When i send a test mail to my mail server i get two mails back in the inbox. 
The same happens with several messages which I get sent from other mail accounts.
With other mail clients this problem does not occur. Do you have an idea what could be the reason, wrong settings, or something similar?

Are you sure this is not some confusion caused by the conversation feature, which lists both the sent and received messages?

Turn off conversations in Menu > View > Conversations and see if there is any difference.

Thanks mr. curtin for your response.
No the conversation feature is not the problem. The doubled messages were only inside of the input box. But i’ve found the problem, i have created two separate accounts inside of eM client, but the accounts are by the same provider (gmx). So the eM client download the mails from gmx from both adresses, so their are doubled in the inbox.
I’ve deleted the second account and add an aliass for the first account with the second adress, now it works perfectly.

Good to hear you got it sorted! :wink: