Is mammary gland are ductless gland?

Yes. The adrenal glands are ductless glands.

Yes

I had done a piece of coursework about the endocrine system and I did find out that the endocrine glands are in fact ductless.

Both of them are exocrine glands i.e. they have duct systems that accept the glands' secretions; milk and sweat.

glandular epithelium