Many factors can effect email delivery - some of which are out of your control.

For example, if you are currently in a shared environment (hosted shopping cart, email service, shared hosting, etc) any one of the other users on the system can affect your delivery.

Every time someone complains of SPAM, the IP address that email came from is recorded. After a large enough number of complaints during a certain period of time, that IP gets blacklisted - which basically means that no ISP or email provider will accept mail from that IP.

Even if you have a dedicated IP, if someone else on the same IP-block causes enough complaints, the entire block of IPs gets blacklisted.

This is just one of the many factors affect email delivery. It’s a complicated game, and your best bet is to allow RelayCloud to take care of it for you.