Mendix Cloud EU (Frankfurt) issue sending email using SMTP relay

We have identified an issue in the region Mendix Cloud EU (Frankfurt). Customers sending email, using an SMTP relay over port 25, might be unable to deliver those e-mails. This issue is caused by one or more of our outgoing IP addresses being blocklisted by an external email security provider. We are in communication with the external email security provider to have the affected IP addresses from their list. Until then, our advice is to switch to a different SMTP relay provider and avoid using port 25 for sending email altogether.