Hi guys, Sorry i need to post. Been doing this for ages and can usually work it out from the forums but my brain is well and truly busted now. I used the migration tool to migrate to another server. old server was debian 8, new server ubuntu 18. also new server is behind nat. I believe being behind the nat is the problem. Users aren't receiving emails from most places. a few get through but most get the error. 4.2.1 Recipient address rejected: Domain not found).. MXTOOLBOX says there is a loop detected and referred back to old servers ip. address. https://www.mailcontrol.com/utility/domain_info.mhtml show the correct records though. Part of the problem may be that I haven't managed to add the external address to an interface of the server. so if I telnet 25 to the record. it trys to telnet the router/gateway. not knowing what its external address is, could be related? $TTL 3600 @ IN SOA ns1.yyy.com.au. admin.yyy.com.au. ( 2019042424 ; serial, todays date + todays serial # 7200 ; refresh, seconds 540 ; retry, seconds 604800 ; expire, seconds 3600 ) ; minimum, seconds ; mx1 3600 A aaa.aaa.aaa.aaa mx2 3600 A bbb.bbb.bbb.bbb xxx.com.au. 3600 A ccc.ccc.ccc.ccc www 3600 A ccc.ccc.ccc.ccc xxx.com.au. 3600 MX 5 mx1.xxx.com.au. xxx.com.au. 3600 MX 10 mx2.xxx.com.au. xxx.com.au. 3600 NS ns1.yyy.com.au. xxx.com.au. 3600 NS ns2.yyy.com.au. default._domainkey.xxx.com.au. 3600 TXT "v=DKIM1; t=s; p=MIGfMxxxxxxZo0evTh8i11QIDAQAB" xxx.com.au. 3600 TXT "v=spf1 mx a ~all" please help. Thanks.