Problem with an interval between letters

Hello everyone! I have a very strange problem - a wrong interval between letters in mails. 
I have made a screenshot to show that.

If you have an idea, how I can fix it, please help!
Thank you!

Hello Dmitry, are you able to replicate this problem on all your received (or sent) messages or just some of the received messages?

What version of eM client are you currently using on your computer, can you please check the release number in Help > About?

Almost on all my received messages I can replicate this problem. If I send a message I haven’t this problem. I have version 6.0.22344

Hello again, can you please send me one of the messages exported into .eml file to my work mail, mcgregor@emclient.com with a reference link to this forum topic?

Thank you.