We are coming from an Exchange 2003 with SBS2003 environment so have no experience with versions other than that prior to using Exchange 2013. We have a new Exchange 2013 installation using the same email accounts we always used. We did setup an MX record for our domain (mail.domainname.com) with the Registrar (in this case, Network Solutions) for our domain when we moved to Exchange 2013.
We have had a very significant increase in SPAM ever since this new installation. Why would that be?
Note with SBS2003/Exchange we had no 3rd party Antispam tools installed..we had very little Spam.
Thanks for any input.