It's a SPF problem, a misconfiguration at bitcointalk
Any mailserver will reject this emails if SPF (Sender Policy Framework) is enabled
current bitcointalk configuration:
v=spf1 mx a include:
amazonses.com -all
But last attempts in my mail.log from:
ec2-52-45-214-107.compute-1.
amazonaws.com
this does not match -> REJECT
May 1 14:30:25 mail1 policyd-spf[19143]: Fail; identity=helo; client-ip=52.45.214.107; helo=[Suspicious link removed]; receiver=xxx@xxx.xx
May 1 14:30:25 mail1 postfix/smtpd[19133]: NOQUEUE: reject: RCPT from ec2-52-45-214-107.compute-1.amazonaws.com[52.45.214.107]: 550 5.7.1 <
xxx@xxx.xx>: Recipient address rejected: Message rejected due to: SPF fail - not authorized