DNS configuration for mailserver

1. Publish a DNS record (MX type) for the domain name instruture.cf
Found this link: https://my.freenom.com/knowledgebase.php?action=displayarticle&id=44

2. Add the following SPF record to the domain instruture.cf:
v=spf1 a mx ip4:186.226.223.233 ~all

3. DKIM key
Selector s20190521507, last update 2019-05-21 14:03:53.

DKIM DNS record:

s20190521507._domainkey.instruture.cf. IN TXT "k=rsa; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA2ZPfm3XP9KKjaB/320C8hBHOG4Sne/Z/4w8N+eeqlRXrNSDV//iIpCwUvpT7i9KfVvMkusO6q95k9FYaGKA5UEyHQwF5rNiAgimfWLytbOCkkd1a9XO3Ana3XsoG2D8eY7N3TY95pq8ZSiPK9V+pYd1jPmE7l96JfIenTQ+DKQd6/iYztMajH9GA5Sp6sTa4hJ4ES/0BtL0n94gc/cGtFxt1d90qh5MUyRbwlzwo4lliu2PRvjOYlxrjhVf05vHHVFrXX0aeY/MjqFWO3t2gZ6HzxD1slVl2eJ9TbKujkWGLMsJ0ERswpg4NNVXQNHPc4jnyZMow4sIBZf+j+FJmDQIDAQAB"