topic Hi Mohammed, in Network Security https://community.cisco.com/t5/network-security/asa-with-exhange-server-problem/m-p/2791214#M173298 <P>Hi Mohammed,</P> <P>Check if the below link helps with your issue...</P> <P></P> <P>https://social.technet.microsoft.com/Forums/en-US/aca4759d-5baf-4e7c-a6b5-ab5528a8e8c6/421-440-remote-server-response-was-not-rfc-conformant?forum=exchangesvrsecuremessaginglegacy</P> <P></P> <P>hth</P> <P>MS</P> Sat, 16 Jan 2016 02:08:13 GMT mvsheik123 2016-01-16T02:08:13Z ASA with exhange server problem https://community.cisco.com/t5/network-security/asa-with-exhange-server-problem/m-p/2791213#M173297 <P><SPAN>i installed asa to publish exchange server and it is working fine , but there is problem they cann't send mail to domain host in linkdotnet company ( ISP company ) and any domain host with linkdotnet isp doesn't work and there is error msg appear "421 4.4.0 remote server response was not rfc conformant"</SPAN></P> Tue, 12 Mar 2019 07:09:03 GMT https://community.cisco.com/t5/network-security/asa-with-exhange-server-problem/m-p/2791213#M173297 mohamed.fawzy2012 2019-03-12T07:09:03Z Hi Mohammed, https://community.cisco.com/t5/network-security/asa-with-exhange-server-problem/m-p/2791214#M173298 <P>Hi Mohammed,</P> <P>Check if the below link helps with your issue...</P> <P></P> <P>https://social.technet.microsoft.com/Forums/en-US/aca4759d-5baf-4e7c-a6b5-ab5528a8e8c6/421-440-remote-server-response-was-not-rfc-conformant?forum=exchangesvrsecuremessaginglegacy</P> <P></P> <P>hth</P> <P>MS</P> Sat, 16 Jan 2016 02:08:13 GMT https://community.cisco.com/t5/network-security/asa-with-exhange-server-problem/m-p/2791214#M173298 mvsheik123 2016-01-16T02:08:13Z hi mvsheik , https://community.cisco.com/t5/network-security/asa-with-exhange-server-problem/m-p/2791215#M173299 <P>hi mvsheik ,</P> <P>this link is not helpful , i tried to put dns of ISP on exchange server but also still the problem not solved.</P> <P></P> <P>br,</P> <P>mohamed fawzy</P> Sun, 24 Jan 2016 12:59:44 GMT https://community.cisco.com/t5/network-security/asa-with-exhange-server-problem/m-p/2791215#M173299 mohamed.fawzy2012 2016-01-24T12:59:44Z