There are various reasons why an email might not be delivered. Before taking further steps, you should check the following points:
If the mailing still does not land in the recipient's inbox or spam filter, it could be due to a server-side firewall and/or spam filter. The server accepts the mail but does not forward it to the recipient's mailbox. This often occurs when multiple emails are sent simultaneously to the same corporate network.
The solution: Ask the company's IT department to add the MAILINGWORK IP addresses or the subnet to the internal whitelist. You can find our IP addresses in our FAQ article.