Unknown address error 550-'SPF check failed

[krishnahutait]

I found the problem when emails were sent to the destination site. Recipient site
users get the error message ’SPF check failed

[Dustin Anderson]

your post is a little vague, so not sure what your asking.

you can use mxtoolbox to test and verity Sender Policy framework(SPF) and other security.

https://mxtoolbox.com/SuperTool.aspx 

[saliyev]

I suggest to get message headers from recipient side to get more information regarding issue.

also sending SPF verification on other recipient domains (like gmail, etc.) by sending test messages