Are informal inquiries about postdoctoral positions liable to be perceived negatively?
Informal inquiries are not liable to be perceived negatively: An informal inquiry is a very good way to make first contact before sending over more formal items such as a CV, letters of recommendation and proposed research ideas. A thoughtful email with some very brief and basic information about yourself and your interest in the potential lab is more likely to be read and replied to (no information overload). After initial contact is made, the more formal process will then be more directed as information about timing and funding may be provided.