Phlebitis is the inflammation of a vein wall, as seen in conditions such as varicose veins. This can't be caused by massage.
There may be instances where you could get a 'skin' infection from massage if the skin has been stretched from oedema and started to crack. That's a whole new route for bugs to enter. So keep the legs clean and dry, apply sorbolene or another neutral moisturiser to prevent cracking.
Lymphoedema is caused by the lymphatic system failing to pick up all of the fluid that has leaked to the 'extra' space around the vessels in your legs. This fluid leaks because of altered plasma proteins (if lymph).
Plasma proteins decrease in malnutrition, liver or renal disease, loss of circulating plasma or leakage of protein into the tissue.
If there's less plasma protein in one place, there's less pull on the leaked proteins to go back where they came from and where plasma goes, fluid goes (to even it out). (put simply).
Lymphatic oedema is firm and doesn't 'pit'. It's full of proteins.
Oedema can be pitting, caused by fluid/water and circulation issues.
Gravity; to drain it back up.
Massage; to push it back up.
Compression; to ease it back up.

Stretches and muscle contraction/release is good if it is oedema caused by fluid back up from heart-lung issues. It pushes and eases the circulation back up the veins past the valves in the vein, 'taking' some fluid with it. (simply).
Different kettle of fish if it's lymph I'm afraid.