TXT records are a type of Domain Name System (DNS) record that contains text information for sources outside of your domain. You add these records to your domain settings. You can use TXT records for various purposes. TXT records are normally used for email spam prevention and domain ownership verification.
SPF gives other mail servers a way to verify that mail claiming to be from your domain is from one of your IP addresses. They do this by checking a special TXT record you put in your DNS records. It is an interesting way to prevent mail spoofing.
DKIM (DomainKeys Identified Mail) is an email security standard designed to make sure messages aren’t altered in transit between the sending and recipient servers. It uses public-key cryptography to sign email with a private key as it leaves a sending server. Recipient servers then use a public key published to a domain’s DNS to verify the source of the message, and that the body of the message hasn’t changed during transit. Once the signature is verified with the public key by the recipient server, the message passes DKIM and is considered authentic.
v=spf1 include:spf.protection.outlook.com -all
MX records are mail exchange records and are used for sending email to your email address. The MX records tell which mail server will receive the incoming emails for that specific domain and where those emails should go.
A records are the most basic type of DNS record and are used to point a domain or subdomain to an IP address.