This is a very common problem that many users report to us. It happens because many mail servers and anti-spam systems let you set up a rule so that any email arriving from the corporate domain is rejected if the sender’s IP is not that of the organization’s mail server or servers. It is similar to SPF, but with this setting the emails are blocked completely in every case.
This is done because spammers often put an address from the recipient’s domain, or even the recipient’s own email address, in the headers to trick them into opening the message by winning their trust. The problem is that tests and newsletters sent from Mailrelay to your own corporate domain will not arrive if this rule is enabled on your organization’s mail server.
The solution is simple, although you will need to talk to your IT department or email administrator. Ask them to whitelist these IP ranges and, if possible, add a rule so that emails arriving with your sender address from any of these IPs are delivered and the blocking described above is not applied.
93.159.208.0/21
185.103.8.0/22
5.56.22.0/24
82.199.156.0/24
91.194.237.0/24
These are the ranges published by our SPF record (spf.ipzmarketing.com).
Another solution would be to disable the rule, but then you risk spam messages that used to be stopped now being delivered. If you have any questions about this, don’t hesitate to contact our Customer Support team.
This kind of problem is usually related to deliverability in email marketing in general, and to how mail servers themselves decide what spam is and how to filter it.