Subject line
The headline of the email — the main thing an inbox shows before it is opened.
The subject line decides whether the rest of the email gets read. It is shown alongside the sender name and the preheader, and on a phone it is truncated far earlier than on a desktop — often around forty characters.
Put the meaning first, so that the truncated version still says something. Trailing words are not read; leading ones are.
The sender name usually matters more than the wording. People decide by who is writing before they read what it says.