File-transfer startup YouSendIt, which allows users to bypass the limits that most email services put on file transfers, announced it raised an extra $15 million in its fourth round of funding on Friday. New investor Adams Street Partners led the round, along with former investors Emergence Capital, Sigma Partners and Alloy Ventures.

YouSendIt allows users to send files sized up to 2 gigabytes through email — though the files aren’t actually transferred via e-mail, but hosted on YouSendIt’s servers and the email recipients are allowed to download them.

But YouSendIt isn’t the only player hosting large files for transfer — RapidShare, MegaUpload and, among others, also offer hosting services for large files.

The Campbell, Calif.-based company does boast 13 million registered users and more than 210,000 subscribers, and reportedly delivers 15 million files a month. Reuters, Salesforce, Rheem and Ritz Camera are listed as clients for the company.

Robin Murray, partner of Adams Street Partners, was named as an observer of the YouSendIt board of directors. The file-sharing company raised $14 million, $10 million and $4.7 million in earlier rounds of funding.