https://www.limilabs.com/blog/sign-emails-with-dkim

https://support.rackspace.com/how-to/create-a-dkim-txt-record/

http://www.mecatronica.eesc.usp.br/wiki/index.php/Verifiying_DKIM_signatures

http://dkim.org/specs/rfc4871-dkimbase.html

 

Quick reference to Internet message headers:

https://www.cs.tut.fi/~jkorpela/headers.html

 

HOWTO define DKIM/ADSP RRs

http://www.zytrax.com/books/dns/ch9/dkim.html#examples

 

Online Test Tool:

https://mxtoolbox.com/SuperTool.aspx

http://www.appmaildev.com/

https://dmarc.org/resources/deployment-tools/

 

DMARC

https://dmarc.org/

https://dmarc.globalcyberalliance.org/

Specification

 

DMARC resource record in the DNS

"v=DMARC1;p=reject;pct=100 rua=mailto:postmaster@dmarcdomain.com"

Tag Name	Purpose	Sample
v	Protocol version	v=DMARC1
pct	Percentage of messages subjected to filtering	pct=20
ruf	Reporting URI for forensic reports	ruf=mailto:authfail@example.com
rua	Reporting URI of aggregate reports	rua=mailto:aggrep@example.com
p	Policy for organizational domain	p=quarantine
sp	Policy for subdomains of the OD	sp=reject
adkim	Alignment mode for DKIM	adkim=s
aspf	Alignment mode for SPF	aspf=r

Refer to

https://tools.ietf.org/html/rfc7489#page-16

 

Google, Microsoft, Yahoo

https://dmarc.globalcyberalliance.org/my-cloud-email-provider-supports-dmarc-do-we-still-need-to-implement-it.html

 

Troubleshooting

Gmail: https://support.google.com/a/answer/3726730?hl=en

Outlook.com: https://mail.live.com/mail/troubleshooting.aspx

Yahoo: https://help.yahoo.com/kb/mail/practices-senders-sln3435.html

AOL: http://postmaster.aol.com/Postmaster.Troubleshooting.php

https://www.mailenable.com/kb/content/article.asp?ID=ME020003