What can professors do to encourage properly written email messages from students? (Motivated by https://academia.stackexchange.com/questions/55082/hey-i-was-wondering-of-your-students-write-like-this)

The writing style probably [stems] from the electronic age of text
messaging. In any case, an email between an a student and professor is
a professional communication (not a social text message).
[Example:] &quot;hey. i was wondering if your students write like this when they send you emails or ask for your help in an email and weather or not your willing to respond when such little effort is put forth when writing.&quot;

What can professors do to encourage properly written email messages from students?
(Other than being a positive role model.)
hey. i was wondering of your students write like this


Alas, yes, they do (however, I'm a non-native English speaker who teaches international students whose level of English is extremely varied, and there's not much I can do about grammar).

Anyway, during the first lesson I give the following pieces of advice (which are frequently ignored, though):


Sender address: please, use your institutional email address and avoid personal fancy addresses like "dirtydeedsdonedirtcheap@hardrock.com". But if you really want to use such an email address, at least configure the email client to show your real name and surname.
Subject: write a meaningful subject: if you don't put a subject and respect point 1, I'll surely delete your email without even reading it, thinking that it is spam.
Course information: please specify which course you are attending or have attended: I teach several courses and if you don't specify this I may not be able to answer (this piece of information is the most frequently missed). 
Express your issues clearly: if you have long questions or complicated issues, just ask for an appointment instead.