== Whoa, that's an underscore in spf. I thought you could only have letters, numbers, and dashes in domain names, no underscores?
| | == Whoa, that's an underscore in spf. I thought you could only have letters, numbers, and dashes in domain names, no underscores?
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Underscores create a new secret dimension: that's the only way to guarantee you don't collide with an existing subdomain. SRV records use underscores for exactly this reason.
Actually SPF doesn't use underscores anymore because, although legal, many providers didn't support them. Other related technlogies, such as [http://mipassoc.org/dkim/ DKIM], do use them however.
| | This is not really SPF-specific, please see [[DNS/Underscore]] for more information.
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