Your email service may have started to require a password for sending emails. Check with your ISP.
I do not understand what you're saying, The grammar does not make sense. Which files are you talking about? PDF files? what are you trying to do? Attach a file (PDF?) to your email? Or are you trying to email PDF from within Acrobat or Reader?
If it is the latter, then tell us as many specifics as you can, including platform (Mac/Win), OS/version, product (Acrobat/Reader), product version, exact sequence of commands that you perform and where the failure occurs. Which exact alert do you get.
If it is the former (you cannot attach files to an email) then ask your ISP provider. This is not something this forum can answer.