When to Start Soliciting Letters
As soon as you know how many collaborators you'll have on the project, you must begin soliciting their letters of support. If you are writing them, you should e-mail your copy to them so they can print it on the organization's letterhead.
As you develop your schedule for completing the grant, add in a checkback point for those agencies that have agreed to write a letter of support but have not yet sent it in. Request that the original letters be sent by mail or courier directly to you or to your client's office. Stress that they should be unfolded and sent in a large envelope. Your other option is to pick them up from each agency.