Email

Email is where you will receive various in-game tutorials, goals, contract proposals, reminders, airport info round-ups, and formerly, spam.

Tutorials
As you begin the game, you will get an email from the city's mayor welcoming you to your airport and giving you tips, as well as emails from the city's Public Transport Office offering help with construction and asking you to build a bus station. These emails are to help new players start.

Purchase Receipts
After the completion of purchases, you will receive an emailed receipt for each purchase.

Spam
Before the R&D update, you would receive many emails titled "Golden Opportunity ! ! ! PAY QUICK" from "Dr William Monroe". These emails could be ignored but were also very annoying. To stop receiving them, you had to purchase an Anti-Spam Filter. This was removed later.

Contract Negotiations
You may get emails about companies wanting to negotiate. If so, negotiate. This is really just a reminder email.