In order to setup your SPF and DKIM records, you need to first login to your Mandrill account, then go to Settings > Domains.

From there you’ll see your domain that you’ve been sending from, and you can click View SPF settings or View DKIM settings. This will show you the exact record that you need to add to your DNS.

SPF:

To enable SPF, add another TXT record, this time for the bare domain you added as your sending domain. Click View SPF settings; the modal will again prompt you to create a new TXT record with a domain name and value.

If you’re only sending mail for that domain through Mailchimp Transactional, the value should be, at minimum:

v=spf1 include:spf.mandrillapp.com ~all

If you already have a TXT record with SPF information, you’ll need to add Mailchimp Transactional’s servers to that record by adding include:spf.mandrillapp.com in the record (before the last operator, which is usually  ?all, ~all, or -all).

DKIM:

Next to your domain, click View DKIM settings. A modal will appear with instructions for setting up DKIM on your DNS provider. Add a new TXT record with the name mandrill._domainkey.example.com (replace example.com with the domain you’re setting up).

The value for the record should be one of the options listed below—some DNS providers escape semicolons for you, while others require you to do it when setting up the record.

With semicolons escaped:

v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCrLHiExVd55zd/IQ/J/
mRwSRMAocV/hMB3jXwaHH36d9NaVynQFYV8NaWi69c1veUtRzGt7yAioXqLj7Z4TeEUo
OLgrKsn8YnckGs9i3B3tVFB+Ch/4mPhXWiNfNdynHWBcPcbJ8kjEQ2U8y78dHZj1YeRXXVvWob
2OaKynO8/lQIDAQAB;

With semicolons unescaped:

v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCrLHiExVd55zd/IQ/J/
mRwSRMAocV/hMB3jXwaHH36d9NaVynQFYV8NaWi69c1veUtRzGt7yAioXqLj7Z4TeEUo
OLgrKsn8YnckGs9i3B3tVFB+Ch/4mPhXWiNfNdynHWBcPcbJ8kjEQ2U8y78dHZj1YeRXXVvWob
2OaKynO8/lQIDAQAB;