For applying to math postdocs on mathjobs, does "N Reference Letters" include one for teaching? I'm a graduate student in the US, currently applying for postdoc positions on the mathjobs website. The format of the job postings is basically a description of the position, followed by


  Application Materials Required
  Submit the following items online at this website to complete your application:  
  
  
  Curriculum Vitae  
  Research Statement
  ...
  N Reference Letters (to be submitted by the reference writers at this site)
  
  
  And anything else requested in the position description.


(where N is usually 3 or 4).

Sometimes, the position description says explicitly


  N letters of recommendation, one of which should address the candidate’s teaching qualifications.


My question

If the position description does not have an explicit statement asking for a teaching recommendation letter, is it supposed to be one of the N letters I submit to them anyway? Or, should I submit N letters all having to do with my research? Is there any harm in submitting N + 1 letters in order to include my teaching recommendation letter?
In my experience serving on large numbers of pure mathematics search committees at a couple of different research universities, people who read the files are often only dimly aware of what the ad requests.  The vast majority of files will contain 4 research letters and 1 teaching letter.  Even if they only ask for 3 research letters, it is a poor idea to not include a 4th if you have one since most people will have 4.

Some people go overboard and submit a ton of research letters (I've seen 8-9 in a single file).  This can also cause problems: 1. usually when someone has that many letters they are not uniformly strong/informed, and 2. it looks weird, sort of like a violation of implicit social norms.  Probably you won't cause yourself problems if you go as high as 5, but don't exceed that.