Reject mail from invalid domains

[John Wilcock]

Jason Ede wrote:
> Surely it makes sense to at least check if the sender is a fully 
> qualified domain and also that there is an MX record for that domain?

In theory, yes. In practice, poorly configured mail servers are not 
uncommon and sooner or later you will end up rejecting genuine mail if 
you insist on this.

Also, consider what will happens if a sender domain's name servers are 
temporarily unavailable. [With postfix, the default reject code for an 
unknown helo hostname is 450 rather than 554 for precisely this reason].

John.

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