This article applies to eM Client 9 and newer.

eM Client 9 introduces contact avatars in the message list, but this can make other details harder to see in a more compact view or on smaller monitors.
You can easily disable the avatar feature or at least resize the avatars to take less space.

Resize Avatars:
Go to Menu > Settings > Mail > Read and scroll down to the Message List settings.
There is an Avatar size: option which you can set to Regular or Small.

Remove Avatars:
Right-click the top of the message list and open Columns configuration.
Select the Avatar from the "Show these columns" list on the right and then click the Remove button, which will move it to the list on the left, "Available columns".