Which exchangess?
Most of the US based ones, like Coinbase & Gemini will close your account if they think funding is coming from a mixer. There are lots of discussions about that happening here and on many other sites.
Other ones, in other parts of the world, who knows. Depends on their mood and how much
BTC.
Also, if you are not doing a straight
BTC -> fiat exchange may be a bit less strict. Where some others, really don't care at all.
As for if it's from a mixing transaction or not. Depends who you ask:
https://bitcointalk.org/index.php?topic=1935098.msg58313016#msg58313016-Dave
Yes I guess that makes a lot of sense as US based exchanges are under very strict scrutiny and pressure to live up to compliance requirements. I can think of a good number of exchanges that wouldn't care at all. At the same time those are also exchanges where you sometimes fear that they might have closed their doors the next morning you wake up.