Colleague and I (diff teams but sit near each other in the office days pre-wfh) started emailing a week ago to organise a birthday. Emails turned into back and forth chat, quite long lengthy emails laughing and joking - he makes my sides split with laughter every email. I'm sure he still has a gf, I am separated (although not sure how public knowledge it is). How can I know if he's actually flirting and it's okay to flirt back (because I do like him but would absolutely stop if I knew he wasn't single)? He compliments me in very fun cheeky ways, asks questions back and forth and puts a bit of innuendo into his emails. I just don't want to read too much into it!