1-grit support is non-existing

We are hosting our services via 1-grit, it seems that for some reason suddenly important emails from our accounting services provider were blocked. We checked all the support articles and added the services provider on the white list of the firewall but still no emails are being received from them. We tested to gmail accounts and other email services and all is working well except to our our email services. I logged an ticket to 1-grit and asked for assistance. The feedback I received was that the services provider were added to the white list (which I did) and it should work.... and the ticket were resolved and closed by their support team without the issue being resolved. Now I'm forced to send invoices via an gmail account to my clients which is extremely unprofessional.