Emails are blank

I send email blasts to customers of a company that often pertain to safety and severe weather information. Recently, I have received several complaints from email accounts about the messages arriving in their inbox but being completely blank when opened. This is not an issue with any other email providers and messages do appear to be opening properly for some email users.

Is this something you've experienced and is there a known issue with email blast messages being delivered to email users blank?

Thank you.