Check out data compression services

A number of services offer data compression and other optimizations for use with satellite phones. Each has it's own set of benefits and downsides; some are only experimental at this point.

UUPlus - Voice: +1 (805) 534-1425, Fax: +1 (805) 534-9502 E-mail: info@uuplus.com
UUPlus has the best compression ratio of any product we've seen. When mail is sent through your POP3 client such as Outlook Express, UUPlus grabs it, bundles it into one message, compresses it, strips off and separately compresses attachments. UUPlus also speeds up the time to connect and begin sending by about 400%! All mail is routed through a UUPlus server where the bundled and zipped files are decompressed, unbundled, attachments are reattached and the messages are routed once more to their intended recipients. Another big advantage to UUPlus is that it works with any satellite service provider. It does not require you to drop your existing satellite services to join a different one with UUPlus. UUPlus has been tested and works with mini-m, Iridium, ACeS as well as some GSM cellular phones and Codan HF equipment.

Stratosnet 1-888-766-1313
Stratosnet has a $30 setup fee when you sign up with Stratos for your satellite services. It includes user software that is easy to set up and is virtually invisible to the user under normal conditions. It compresses data on the fly and sends all data through the Stratosnet server where it is decompressed and forwarded to it's destination. Although I have not yet tested it, it boasts that it will save 75% of your online e-mail time. The biggest downside to Stratosnet is that you can only use it if Stratos is your service provider. Stratos is a good service provider and they will match Comsat's industry leading humanitarian rate but switching service providers can be difficult and requires careful research and comparison.