If you're talking about where the pipe goes into the flange, I'd say it should be glued, as evidenced by what appears to be glue on the pipe, if you're talking about where the flange connects to the tank, I really have no idea, never had to get that far.
What ever it is, if I had a leak there, I'd gladly pay someone to fix it.
2007 Forester 2941DS
2014 Ford Focus
Zamboni, Long Haired Mini Dachshund