Issue SPF validation Failed, but why?

[Thera]

Server operating system version

Debian 9.13

Plesk version and microupdate number

Version 18.0.44 Update #3

Hey there, i got a new customer in my Server and they got a lot of Problems with incoming Mails. I cant find the Reason. new SPF record set This Morning from -all to ~all

Can you help me?

Thank you!

said: 550
5.7.23 SPF validation failed. : Reason: default (in reply to end of DATA
command)

 

[Thera]

Hey there, i got a new customer in my Server and they got a lot of Problems with incoming Mails. I cant find the Reason. new SPF record set This Morning from -all to ~all

Can you help me?

Thank you!

said: 550
5.7.23 SPF validation failed. : Reason: default (in reply to end of DATA
command)

Domain is bestminutetravel.com

 

[GwenDragon]

https://support.plesk.com/hc/en-us/articles/360020781639-Unable-to-receive-mail-from-external-domain-5-7-23-SPF-validation-failed

 

[Kaspar]

Hey there, i got a new customer in my Server and they got a lot of Problems with incoming Mails. I cant find the Reason. new SPF record set This Morning from -all to ~all

An SPF check is always performed against the server of the sender. If your customer has issues with incoming email, changing the SPF record of the domain of your customer does not have any effect. As the issue is (most likely) at the senders domain, which you have no control over (unless it's a domain you own/manage as well of course).

None the less, the link posted by @GwenDragon contains some useful options you could consider.