Does a carrier have to be a DAT customer to send a private load to them?

There is no indication that you will receive alerting you to whether the email address was valid or whether it was received.  As a broker or shipper offering loads through Private Network, you must ensure that the email addresses you have on file for your carriers are accurate.

If a carrier has not been receiving your loads through email, ensure that you have the correct email address on file and have them check their spam/junk folders in case their email server flagged the email as spam.