We have just switched our internet connection from cable to fiber. This required a public IP address change. I updated the MX records with our domain host but I am now getting 442 4.4.2 Connection Dropped errors. Not all mail is doing this but a significant amount. I have several iPhone users who are now not getting mail on their phones but other iPhone users do. I realize it takes a little while to propagate the servers with the new records but it has been over 6 hours. Any help with this would be appreciated.