German phrase
Ich melde mich wegen ~.
Meaning
I'm contacting you about ___
When to use it
It states why you are writing. It suits formal emails and official requests.
Example dialogue
Ich melde mich wegen der Kursanmeldung.
I'm contacting you about course registration.
Bitte senden Sie die Unterlagen per E-Mail.
Please send the documents by email.