For an e-mail to lecturers, always use the TU-Dortmund e-mail address. If other e-mail addresses are used, they may be intercepted as spam or ignored due to "joke addresses". Furthermore, the official e-mail address serves as authentication that the person writing is actually a member of TU-Dortmund.
The specification of a concrete subject in the line "Subject" is of great importance. Express the concern of the e-mail here in a few words so that the teaching person can assess the urgency of the e-mail at a glance. Keywords such as "Course meeting on date, Seminar paper in course ..., BA thesis, Examination course title on date" should be used.
If the lecturer has not explicitly refused to be addressed by academic degree or title, these are always used for professors and doctoral candidates, whereby Professor is to be written out in full, while Doctor is abbreviated to "Dr.". In the case of persons with several titles, only the highest is to be mentioned. PD (Privat Dozent) is neither an official title nor an academic title, so it should not be mentioned in the salutation. The form of address for people with a title should be: "Dear Title Surname", while people without a Title should be adressed as "Dear Mr./Ms. Surname" If you are not sure about the gender of the person you are contacting use "Dear first name Surname".
A precise assignment of the request to a person, an event or an examination can reduce the response time enormously. Therefore, depending on the context of the e-mail, the name of the course, the LSF number of the course, the date of the examination, the relevant semester and the matriculation number should be stated.
Length of the e-mail
E-mails should be written according to the principle "as short as possible, as long as necessary". The subject matter should be presented briefly and no embellishments should be used. More complex topics are often better discussed in a consultation or telephone call.
An e-mail should end with a formal greeting, the most common being "Yours sincerely" followed by a paragraph and "First name Last name".