Problems sending emails to recipients using Microsoft Outlook.

I send emails to multiple recipients using Microsoft Outlook (2010/2013). But a lot of them can not read my e-mails. Outlook displays an error and then quits.

I thought it might be Outlook problem, but this problem only occurs when sending emails from the eM Client (Version 7.0.27943.0).

I need help solving this problem, does anyone have any suggestions?