As a connected genealogist I subscribe to many email lists, forums and blogs related to my interests. Greeting a full email box each day does not perturb me as I can quickly scan the subject lines of the emails,delete those that are not relevant and open those that may be of interest. Some people, however, just don't get it.
Particularly relevant to people downunder is the myriad of Rootsweb Mailing Lists, each of which is devoted to a particular niche area of the field. There are a number of Australian lists to which one can subscribe and connect with people with similar interests.
On one such list last night I eagerly opened a message whose subject line was one word,my given name, thinking that it was a personal note to me. It was for another person who shares my first name.
In all messages is is useful and polite to clearly state, in the subject line of the email, clues to the content of the message that follows. A recent message on The OrangeBathurst list has the subject "John Henry Williamson of Boronore", this clearly tells users about the subject ot the message, however other posts entitled "The New Family" give very few clues. Sinilarly this subject line "[HHHV] Hawkesbury pounds and poundkeepers 1855" from the HillsHawkesburyHunterValley list is very specific, whilst another heading "Wills" is far too general.
List etiquette would suggest that a list is not the place for personal messages. Sometimes, however, it is not possible to contact another list member because of a dead email address. In these cases something like "Personal message to Mary Jones" ,"Trying to contact Fred Wright" or "John Brown - please contact sender" would alert other listers that the content of the message is personal.
Sometimes during the course of a thread (or email conversation) the subject changes. Do not let an irrelevant subject stand. Change it to reflect the contents of the messages in the conversation. Search engines, such as Google, index the contents of mailing lists; it pays to have relevant subjects so that your posts can be indexed correctly and subsequently found by others.
Busy people may skip emails with fuzzy headings such as "genealogy question" or 'help please"; if you want people to read your messages remember to have a clear and cogent subject line.