hi Paul, Mesaïeux is useful for research to get records, since they do have a lot of them, but they should not be cited as source without much more data added, since they are a pay-site also, and for someone to view their records they have to pay for it. Operates a bit differently than most places, you can build your tree there for free, but to consult the database and get records you have to pay. Not very expensive individually I'll grant, but it accumulates after a while.
That said, they do have some errors, used them myself for a while, they had my great-grandfather married to Valérie Brissette and remarrying to my great-grandmother after. Trouble is, Valérie's husband died before her. His actual wife was Vitaline Brissette. After I found the relevant records, I sent them copies, and got the answer that the marriage with Vitaline was in a parish for which they did not have the records. Hence the tie-in with Valérie. Which they still have not corrected in their database.