You can use the SailMail system itself to receive text or grib weather forecasts at no charge. The easiest way (free) is to use SailDocs.com For information send an empty email to firstname.lastname@example.org
Several commercial services format and email grib weather forecasts for a fee. PredictWind, Squid/Great-Circle, Grib.US, BuoyWeather, Ocens, MaxSea, MovingWeather, Météo-France, and many others are in that business.
You can use SailMail to communicate with a meteorologist or commercial weather service (e.g. Commanders Weather or WeatherGuy), who can advise you on reasonable departure dates and routes, and can send you periodic routing advice during your passage. We highly recommend this, particularly for new cruisers who have not yet become confident in their ability to interpret weather data.
Finally, there are fax weathermaps and SITOR text weather forecasts that are broadcast by the US Coast Guard and by other HF stations around the world. Your SCS PTC-II modem can be used in conjunction with your laptop to receive these broadcasts.