To ensure all advertised services available on mx1.mailchannels.com & mx2.mailchannels.com are also available on your own mail server(s) which become the downstream record, target hosts. If the MailChannels MXs advertise a service, your mail server(s) must also have that service enabled.
Step 1: SMTPUTF8
SMTPUTF8 is required for inbound domain filtering.
MailChannels MX relay servers negotiate with the sender at the time of receipt and cannot renegotiate with your servers if you do not support UTF8 at the time of delivery.
If SMTPUTF8 is not enabled on your downstream server(s), any message negotiated using UTF8 is returned to the originator as undeliverable.
Enabling SMTPUTF8 in your server is software specific and can differ from one to another. Please see your mail server official documentation for instructions. Generally this setting is enabled globally.
If you would still like some assistance, send a note to firstname.lastname@example.org with your questions and our 24/7 support staff will be happy to help.