1. Login to your own DNS manager.
2. Click Add Record then select TXT to specify your SPF record and then Add record.
Name: Your domain name (domainname.com)
Type: TXT
TTL: 3600
RDATA: Your SPF record data
How to get SPF record?
Login to your cPanel > Go to Email > Click on Email Deliverability
Next click Manage 
Then COPY the record to add into your DNS management.
Example of SPF content as a TXT record below:-
Dedicated Server/SSDVPS: v=spf1 a mx ip4:x.x.x.x ~all
Shared Hosting: v=spf1 include:se.mschosting.com -all
5. Next to add DKIM record
Name: Your domain name (domainname.com)
Type: TXT
TTL: 3600
RDATA: Your DKIM record data
How to get your DKIM record
cPanel : https://veecotech.freshdesk.com/a/solutions/articles/22000287036
Plesk : https://support.plesk.com/hc/en-us/articles/115001027705-How-to-check-if-DKIM-is-working-on-a-domain &
https://support.plesk.com/hc/en-us/articles/115000214973-How-to-get-the-DKIM-public-key-from-Plesk-if-DNS-is-not-installed-
6. While for DMARC, it is standard. Three common options for recipient server to handle mail from your
domain that fail SPF validation.
None: v=DMARC1; p=none; sp=none; rf=afrf; pct=100; ri=86400
Reject: v=DMARC1; p=reject; sp=none; rf=afrf; pct=100; ri=86400
Quarantine: v=DMARC1; p=quarantine; sp=none; rf=afrf; pct=100; ri=86400
None : Will just monitor the DMARC results and you do not want to take specific action on all the failing emails.
Quarantine : Put the emails which fail the checks in quarantine. Most of these emails will end up in the junk folder of the receiver.
Reject : Reject all emails that fail the DMARC check. The email receivers should do this on SMTP level. The emails will bounce directly in the sending process.
NOTE:
Please be advised that this DMARC record need to be added as subdomain _dmarc
Dedicated Server/SSDVPS: For Dedicated/SSDVPS kindly contact our support back to enable from backend.
Shared Hosting: Already enable when you add the domain to the hosting.
Can verify the record by using this online tools
https://www.appmaildev.com/en/dkim/
Click on Next Step > It will generate an email for you send email to the test-2394ff92@appmaildev . com > Copy the email then kindly send from your email domain to the email test-2394ff92@appmaildev . com
Below result will show the result success record added and passed.
