Some destination mail servers perform Sender Policy Framework (SPF) checking therefore emails sent via TMEMS outbound filtering are getting blocked by those destination mail servers.
To resolve the issue:
- Go to the DNS configuration of your domain and create a .TXT record.
- Insert the SPF record syntax for TMEMS outbound servers:
For all regions:
v=spf1 include:spf.tmes.trendmicro.com ~all