It's always a good idea to whitelist your email domain so that emails sent are not rejected. When you add your organization's email address in the Campaign Settings > Email Options > Admin (From) Email Address section, the emails sent by the system will have you as the sender.

There are 2 methods to ensure your email domain is whitelisted:

1) Remove the SPF record for your root domain in your domain settings. You can find this record in your DNS zone files.

If you do not have an SPF record, there is nothing that needs to be done.

This is not the preferred method since we recommend having an SPF record to prevent spammers from sending messages with forged From addresses on your domain.

2) Add to your SPF record. 

For example, if your record looks like this:

v=spf1 a mx ~all

After adding to the record, it will look like:
v=spf1 a mx ~all

If you do not have an SPF record for your domain you should create a TXT record with the value:

v=spf1 ~all