About outsourcing mail reception services
If you are somebody who habitually receives abuse complaints from random third parties, consider twice before outsourcing all your mail reception to third parties such as Google or Microsoft.
<person@ESP_domain>: host ESP_domain.relay1g.spamh.com[220.127.116.11] said: 554 5.7.1 URL/Phone Number Filter - CUSTOMER'S_DOMAIN (in reply to end of DATA command)
Even your own spam filter thinks your customer is a spammer. So you don’t get the complaints. Brilliant.