The minimum recommendation to improve deliverability of your email is to use SPF records. However to improve deliverability further we also recommend setting up DomainKeys Identified Mail (DKIM).
DKIM is another open standard initiative to authenticate email in addition to SPF. It uses cryptographic techniques to authorise whether an email message has come from a valid sender. More and more organisations are using DKIM for authenticating senders. Adding DKIM for your domain will improve deliverabilty to all the domains that have already adopted DKIM.
We will generate the DKIM keys for you, and setup the private key on Black Pearl Mail servers. All you need to do is add another TXT record to your DNS, which we will provide you.
Note, if you are also sending email from other systems (such as internal servers or third party email marketing providers) we recommend you also setup DKIM with all those systems. Otherwise the email being sent from these servers may be less likely to be delivered.