The phrase "a formal email" is correct and usable in written English.
You can use it when referring to an email that follows professional standards and etiquette, typically used in business or official communications.
Example: "Please ensure that you send a formal email to the client regarding the meeting schedule."
Alternatives: "a professional email" or "an official email".
Your tour is not confirmed until you have received a formal email to that effect from the Center.
Several years on, I can't say there has been much benefit from bringing work and personal spheres together on Facebook, perhaps bar the odd occasion when I've been able to message someone I didn't have a formal email address for.
In each wave, the survey request was sent in a formal email from the research team represented by the survey coordinator at Nanjing University.
In a formal email to the resident adviser he spoke with earlier, Clementi summarizes the incidents on Sept. 19 and 21 and quotes Ravi's Twitter account.
In class, students were taught many topics, ranging from how to write a formal email to the importance of turning off their cell phones and taking off their headsets.
If you're sending a formal email, type your full name after the complimentary close.
Alternatively, you wouldn't want to send an overly formal email to a very close colleague.
Once the dust settles, we (the Site Managers) will probably be sending out a more formal email message describing the failure, our response to it, and how we plan on avoiding such failures in the future.
Upon acceptance into the program, you will be provided a formal invitation email with a link to submit the $1,000 deposit or full tuition payment to hold your seat in the program.
These are questions the police now appear to be asking, to judge by their current round of interviews, using the rather limited tools of overseas phone calls and formal email questionnaires.
Less formal email and telephone interviews that complemented the face-to-face interviews occurred during the following year.
