Register is how formal or informal a piece of writing is. A skilled writer modulates it inside a single email — a careful opening sentence next to a plain follow-up, a precise technical phrase next to a casual aside. Model output tends to lock into one register and hold it for the whole message.
The most common failure: stuck on formal
Models default to formal because formal is safer on average. The result is an email to a colleague you've worked with for three years that opens with "I hope this email finds you well", thanks them for their "continued partnership", and closes with "warmest regards" — when the real exchange should have been four sentences and a question mark.
Match the recipient, not the template
- Cold outreach to someone senior — formal, short, with one specific reason for the message.
- Reply to a colleague you talk to daily — first-name, contractions, no preamble.
- First message to a new client — warm but unambiguous about the ask.
- Internal status update — direct verb in the opening sentence, no greeting at all if the thread is already going.
Before
Dear Sarah, I hope this email finds you well. I am reaching out to follow up on our previous discussion regarding the Q3 deliverables. I would greatly appreciate it if you could provide an update at your earliest convenience. Warmest regards.
After
Hey Sarah — any update on the Q3 deliverables? Happy to jump on a call this week if it's faster.