Choosing between tu (le tutoiement) and vous (le vouvoiement) is a real skill in French working life. The safe default is vous with:

• your manager and anyone senior — until they suggest otherwise,
• clients, suppliers and anyone you're contacting for the first time,
• older colleagues you don't know well.

Many teams say tu among colleagues of the same level — especially in start-ups, tech and creative jobs — while law firms, banks and public administration tend to keep vous.

Two everyday combinations: vous + first name is common at work (Marina, vous pourriez…?), and Madame / Monsieur on its own, without the surname, is perfectly polite: Bonjour Madame.

To introduce someone: Je vous présente Manon. — Let me introduce Manon.