We are currently running a trial to investigate the effectiveness of some advertising on Guest accounts only. Paid subscribers will remain free of advertising. If this trial is successful, we hope to be able to be able to invest the revenue gained back into the company to improve our services and features.
We're using single-line text advertisements, so there are no graphics to slow things down.
Currently we're only showing advertising for FastMail.FM features and upgrades, but once we're confident that the mechanism is working properly, we'll be introducing external advertisements.