I would like to protect my customers by SPF checking - no problem. But I know that some of them (believe or not) wants all mails. Is there sometrick how to exclude selected recipients or whole domains from SPF checking? THX for any hint.
Turn off the "enable greylisting" checkbox in the mailbox settings. There is no way to do that for an entire domain; I don't remember if there is a feature request to do so, but you could create one if needed.
If I understand correctly. Turning off the "enable greylisting" means: do not process Greylisting and SPF checking and (maybe others) protections for incoming messages this mailbox?