If you configure Copernica, while setting up a sender domain, you have to make changes to your DNS. DNS is the worldwide system used by computers to change domain names into IP addresses used by computers.
If you want to use Copernica's suggested DNS records you need to know who your DNS provider is. This is often the same company that hosts your website. It might also be the organization where you registered your domain name or handles your incoming email or some other party entirely. You can tell your provider to change your DNS settings. There is often even a web interface where you can do this yourself, but you might need to email them your settings.
If you go back to the configuration screen in the dashboard you can see if your current setting are correct. There are several checkmarks that should be green. Red crosses indicates errors and orange triangles indicate warnings, both indicating your current settings are not entirely correct.
DNS is more than changing a domain name to an ID. It is also a way to request information about a domain name, some of them pertaining to email. The following list contains some of them and links to their respective background articles.
- MX: The server that processes incoming mail for a domain.
- SPF: The IP addresses that send email from the domain.
- DKIM: Used to determine validity of the digital signature.
- DMARC: Policy on (possibly) incorrect email.
All of this can be configured in your DNS. Every time a server receives an email from your domain your DNS is queried for SPF, DKIM and DMARC to determine whether this email is correct and actually coming from you. If an email is sent to you the MX record is requested to determine where to deliver the message.
This explains the large amount of DNS records that should be set when sending email with Copernica. This is because Copernica send email coming from you and should be treated as such. Copernica is also (in many cases) receiving some of the email sent to your domain, namely the bounces.
DNS is a distributed system that consists of millions of nameservers worldwide. Each of these server has a very small part of the database, as there is no server big enough to contain all domain names in the world. This is why a DNS lookup might take some time; some DNS lookups can't be answered immediately and are sent to another (higher level) server.
Because most of the information in a DNS changes very little DNS servers keep a cache. They save the answers to earlier queries so they can answer next time.
If you'd ask, for example, for www.example.com then your device performs a DNS lookup at the server of your provider. The DNS server of your provider first searches its cache to see if anyone queried the IP of www.example.com earlier. If this is the case the answer can immediately be sent to you.
If the address is not in the cache the provider looks the address up in a higher DNS server. This server might know the answer, or refer to another server that knows more about this type of adresses. If a lookup is used very little, for example because it is a little-known domain from a country far away, multiple refers and lookups are required before the DNS server manages to answer and refer you to the correct page.
Thanks to caching most DNS lookups are extremely fast, because often used domain names are nearly always in the cache. The downside to caching is that you can't always see your changes immediately. Even if you update the settings of your domain name in your own DNS server and everything seems to be working well it is still possible that other server still have your old settings. These old setting can be used for queries to this server.
You can determine for each DNS record how long it can be kept in a cache. This is often called the time-to-live or TTL and is often set to a few hours, but a TTL of 24 hours is not exceptional. Therefore it is always smart to wait a few hours before using your new settings.