Is it okay to switch languages in an email? I am emailing a professor I have not met about a foreign exchange program. They teach Japanese, and I started out by writing my email in Japanese only to get halfway through and realize I would have to look several things up if I intended to continue writing it this way. I regularly email my own Japanese professors in mixed languages and I know a few classmates do as well, but we also personally know our professors due to the small classroom setting of the course.

Would it be bad/particularly unprofessional to switch to English as necessary throughout my email?
If any of you are professors, how would you feel if a student you do not know did this? I wonder if it is annoying to them..
It would be weird to see an email in multiple languages, but it's not completely unusual or unheard of. It would certainly make me wonder what's going on if I received such an email, but it's not a breach of etiquette.

In my own personal experience, I had a lot of communications in German. In some cases, if someone was quoting something, or using terms that are hard to translate, they'd throw in the English and then keep on using German.