There are several different aspects that are usually addressed in the quest to stay professionally based with online dealings. The individual has the advantage if professionalism is extended and perceived to exist.
Perhaps the first area that professionalism should ideally cover is the area of etiquette. The universally accepted common elements would include having the semblance of being polite, being able to address each situation with a level of sincerity, working towards creating satisfies customers and many more.
Taking the time and effort to consider the subscriber list or group as a whole and addressing them as if each one was an individual concern and special would allow the positive basis of the relationship to be built.
Making a positive impact is also another way of portraying professionalism. When the other party is assured that the concerns will be addressed and then ensuring the follow up procedures are followed will create the level of professionalism that few can refute.
Using email addresses that are appropriate and professional sounding is also necessary if one want to be taken seriously in the business arena. Simple but often overlooked is the need to ensure all content is accurately written and factual.
Using a suitable descriptive subject line is also a way to showing professionalism and avoids being identified or classified as spammers who also have casual addressing choices. Being specific, clear, reasonable and to the point is also showing professionalism as most people do not have the time or inclination to entertain unsolicited interruptions.
The items included in the signature should be of a professional design and content. Unnecessary information should not be included as it would not be deemed necessary.
Ensure all communications is done professionally and with only information sought exchanged. Keep all exchanges short, accurate and to the point.