It’s hard to guess what “everything” is means. Using the free Gmail for sending mail is against their terms of service. We’re you using regular Gmail? It’s pretty hard to get Google mark configured even if you are paying for it; there is a #howto for that, I believe, but I can’t find it quickly.
Jay, you are right, I tried everything except MailGun and Mailgun just worked. I input the settings just like i did with every other platform I attempted and Mailgun just worked. God bless you and thanks