I noticed an incoming email from a new domain (SPF and DKIM are all set up) has been rejected by mxroute.com:
host ocean dot mxroute dot com [195 201 59 214] said: 550
“The mail server detected your message as spam and has prevented delivery.”
(in reply to end of DATA command)
Since it’s no more possible to actually open a support ticket at mxroute.com user panel, how shall I handle this?
You can whitelist senders and domains under Spam Filters in cPanel. If you feel like this should have been avoided, send me the sender and recipient in a message on chat or a private message on here.
In this case it was a new TLD that must have had a crazy promotion, because I saw millions of spam emails with what appeared to be a 100% spam rate (0 legitimate emails identified). In such a rare case, I tend to block the TLD. This tends to only be new TLDs that no one would be likely to use professionally upon their release, and that match that exact scenario (probably 3-4 to date, .icu was the previous one). Inevitably, one customer goes out and purchases one domain with that TLD later and I have to revert. I’ve done the reversion, and it will take about 1 hour to propagate to all servers.
At least in the time in between I was able to block an enormous amount of spam (over 200,000 since last log rotation).
Just to confirm that email from the domain in question now passes through. Thanks.
Adding the sender to whitelist didn’t help.
Looks like your mail system marks all new domain’s messages as probable spam on entry, it just doesn’t reach the per-domain SA.
If that’s standard reaction to all new domains, I might be missing quite a number of messages without even knowing that.
Note: I sent a test message from the same domain to a GMail box, it went through without a problem.
There are no inbound anti-spam systems that take into account the age of the domain which are utilized by MXroute 
Thanks. I assume it’s possible to use kind of domain-level whitelist while blocking the rest, if they are so much a nuisance.
NB: in the mail system I maintain greylisting mostly works in such a case. But of course every postmaster’s approach is kinda unique.