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If sending email as user@mydomain.com from mail server 1.2.3.4, and the SPF record of mydomain.com set as

"v=spf1 ip4:1.2.3.4 -all"

Will a PTR record do any good? Is PTR required for some e-mail servers to accept my e-mails, or is this SPF record sufficient for delivery purpose(without putting DKIM & ipv6 into consideration)?

  • Are you asking about an SPF PTR record, or a DNS PTR record? – MadHatter Jan 12 '17 at 16:42
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Some mail servers will reject connections from IP's that don't have a PTR record. SPF doesn't change that behavior.

  • Thanks for answering. How will those mail servers behave if server 1.2.3.4 send e-mails as user@otherdomain.com that has SPF points to 1.2.3.4, but not A/PTR records? – Zeno Moson Jan 12 '17 at 17:06
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To extend longneck's perfectly good answer slightly, you cannot control what decisions the admins of other mail servers make about which emails to accept, and which to reject.

Some servers will refuse connections from servers that have no PTR record. Others will use the lack of a PTR as one of a number of inputs to a weighted decision about whether to refuse a connection, or to consider content from such a server to be spam. Any of these strategies can also be applied to servers which cannot be circularly-resolved - that is, when the hostname returned by looking up the server's IP's PTR record cannot in turn be resolved to get back to the IP address.

Most of these strategies are unaffected by the sender domain of a received email, which would in turn affect the choice of which SPF record to consult. So no amount of messing around with SPF records can help you deliver to a server which has decided to take against your sending server on the basis of its lack of a satisfactory PTR record.

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