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How do I set up SPF and DKIM on Linux?

SPF is pretty straight forward if you know how to add TXT DNS records.

But the syntax can be confusing.

Here is a sample record that adds an IP and Outlook settings:

“v=spf1 a mx ip4:xxx.183.121.155 include:spf.protection.outlook.com -all”

Don’t ask what the difference is between – and ~, but just take it as the most confusing parameter ever.
The difference between the dash and the tilde is:

The tilde and dash identify they different types of failures. Consider a message that doesn’t match the parameters specified in the SPF record. Tilde is for a softfail, the message will be accepted and marked if it doesn’t match parameters specified. Dash is for a hardfail, the message will be rejected if it doesn’t match.

https://serverfault.com/questions/663087/what-is-the-difference-between-all-and-all-in-a-dns-spf-record

DKIM guide is quite intense but if you follow the exact guide below, and the tip, then you will be good.

Reference:

https://philio.me/setting-up-dkim-with-sendmail-on-ubuntu-14-04/

If you don’t have a listener on port 8891, then follow the last answer on this post, the one about¬†ExecStart

https://serverfault.com/questions/863468/milter-opendkim-error-connecting-to-filter-connection-refused-by-localhost

How to test? Well, when you’re done, send a message to Gmail, reveal entire message, and then look for PASS x 2.

Other guides:

Google SPF:

https://support.google.com/a/answer/33786?hl=en

SPF

https://mediatemple.net/community/products/dv/204404314/how-can-i-create-an-spf-record-for-my-domain

Include more than one SPF (DON’T ADD 2 X TXT!!!)

https://serverfault.com/questions/283125/how-to-include-multiple-domains-in-an-spf-txt-record

Office 365 @ Go Daddy

https://docs.microsoft.com/en-us/office365/admin/dns/create-dns-records-at-godaddy?view=o365-worldwide

Google DKIM:

https://support.google.com/a/answer/174124

https://support.google.com/a/answer/180504

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