Hello,
If we check the IP through https://www.sophos.com/en-us/support/ip-address-lookup it shows that is OK, but if try to send email to sophos clients it is refused with:
554 5.7.1 Service unavailable; Client host [xxx.xxx.xxx.xxx] is blacklisted. Visit https://www.sophos.com/en-us/threat-center/ip-lookup.aspx?ip=xxx.xxx.xxx.xxx to request delisting
