How to get professors to reply to my email of inquiry for research opportunities / Co-Advising I am now in a thesis-track Master's program and will be applying to PhD next year. Now I want to do some research projects with some of the professors who have areas of interest that I am also interested in. There are only 2 (or 3 if you count in another one who only publish 2 papers in this area in the past 10 years) of them listed under my program right now as other people retired or moved. I already sent 3 emails (including follow-up emails) to these two professors respectively, and they don't seem to be replying at all. I don't know if I should continue to send more follow-up emails - I want to but I am worried that this might be annoying. I am sure that they are not on sabbatical nor stopped doing researches at the moment, so is there anything that I can do at this moment if not finding advisors in another area? Would attending the same conference with them, pretending that I bumped into them help, and then starting a dialogue be a good idea at all?
Also, how does co-advising really work? Is this some request that students actively make with two professors, or is this some request that professors make for students?
EDIT: I did not see &quot;3 emails&quot; when I originally answered the question.  I thought we were talking about 1.
In light of that, it seems probable that they are not interested or don't have an opening. There is a chance they are just busy, but seems unlikely.  You could wait a month or so and e-mail again, but unlikely to get a different result.
You should either look for different professors, or start looking around for other schools that have good programs and email them.