Interfolio is a paid service that will store your letters indefinitely and allow you to upload them to the following application systems: AMCAS, AACOMAS, AADSAS, and TMDSAS.
As soon as you create an account, you can enter letter writer information and they will receive an e-mail from Interfolio with a link to the upload page.
Begin by clicking on the "Request a Letter" link.
You will be prompted to fill out some information about your new recommendation request. This includes information about the recommender and will allow you to add a due date for the letter. You have the option to include a message for the recommender, and you can also upload your CV/Resume and any additonal documents you would like to provide.
Once you have completed the forms and clicked "Send Request," your letter writer will receive an email with an upload link.
When your letter writer clicks the link in the email, they will be taken to Interfolio's website and will be able to see the details of the request and upload the letter.
You should always waive your right to view any letters of recommendation, including those uploaded to Interfolio. As a result, when letters are uploaded, you will receive a notification that the letter is stored in Interfolio, but you will not be able to open the file and read the letter.
Once your letters are in Interfolio you can follow their step-by-step guide for how to upload letters to your application system.