Hello,
a lot of mails have displayed a logo in the inbox before the email information, for example a EBAY logo: 
What must i do, that my own logo is displayed in the inbox at the recipient ?
If you want your own Avatar icon next to your sender email address for recipients to see, then the easiest way is to create a free global “Gravatar” via https://gravatar.com/ and upload whatever image you like for that Avatar. Then link that to your email address, which will then show next to your sending email address in eM Client.
Or if you have your own Domain fav icon avatar linked to your email address, eM Client will also show that next to your sender email address. See this link for info on how to set that up - How to Add a Favicon to your Site - QA @ W3C
Also see the following eM Client support page on how to setup a Gravatar and Domain Fav icon.
Lastly if you have an existing eg: Gmail account or Outlook account with an Avatar, eM Client will show that next to your sending email address if that same account is added into eM Client.