email migration

Am I required to transition Comcast email over to yahoo?  If so, when is the cutoff date?   Who stores my email data when I migrate - Comcast or Yahoo? Will comcast email  system eventually be phased out, eliminating access altogether, except via Yahoo email?  If I don't migrate now, will I eventually lose all my comcast email accounts completely?  I switched one account over.  Now things I could do and see with my Comcast emails, I cannot with Yahoo.  I purposely had only 1 large file over 25M.  When Yahoo told me my migration is complete, I never saw an email indicating what happened to the oversize email and where I can recover it.  All the Yahoo ads makes it less accessible and enjoyable. Unless you pay for the ad free version, which is what they want you to do.  I hear the SPAM filter is extremely aggressive and you cannot change it or turn it off.  I now question making the move is worth it.  I have been a comcast customer for years, paying a lot but willing to for my emails.  If I switch to Yahoo for the rest of my email accounts, then I don't need to keep paying those high prices if I can access email other ways.  Please let me know what options are available and the future of Comcast email.