In 1974, he met Marc Blondel, a prominent figure Workers' Force (FO), a trade union confederation.

[1] Initially, Mailly's critics claimed that he relied on the support of the Trotskyist Workers' Party, although this proved not to be the case.

He started by meeting the leaders of the other main national union federations, breaking with FO tradition, and campaigned alongside them in protests against a new hiring contract in 2005.

His successor, Pascal Pavageau, published details of Mailly's salary and expenses, which proved controversially high.

[3] Following his retirement, Mailly formed the company JCBC Conseil, to advise on social, economic and industrial matters.