Unavailability of the mail service.

Problem solved

The issue has now been resolved, and specialists are monitoring the service.
To connect to the mail gateway, use smtp.servercore-smtp.com. You also need to update your SPF record:
TXT v=spf1 include:spf.servercore-smtp.com ?all

At the moment, there is an unavailability of the mail service via the SMTP protocol at smtp.servercore.mx

Our specialists are aware of the problem and are working to solve it.