This sounds like a formal business email or an important email but I don’t know your relationship to speculate or even the nature of the email to say if this greeting is appropriate or not. I’ve never been in this position but you may want to check out these formats below to play it safe. Probably the content is most important and you will get some western forgiveness. You could add 教授本田先生(or 様). You may want the company name of the CEO as below:
Example
株式会社 社長〇〇様
教授 〇〇様
突然のご連絡失礼します。私、〇〇(work place or school)の〇〇(your name)と申します。