DKIM & SPF Setup for Mimecast

To set up or edit your SPF record, you will need to add: include:_netblocks.mimecast.com

Edit existing SPF record

1. Log in to your DNS hosting provider
2. Look for a TXT containing v=spf1
3. In your existing SPF record, you will append include:_netblocks.mimecast.com
4. For example, if your existing record looks like v=spf1; mx; ip4:1.2.3.4; you would add the above include as follows v=spf1; mx; ip4:1.2.3.4; include:_netblocks.mimecast.com

Create a new SPF record

1. Follow the instructions from our How to Create a New SPF Record Guide.
2. In the Value field, enter: v=spf1 include:_netblocks.mimecast.com ~all and Save the TXT record.

Records for Subdomains

If you are creating a record for a subdomain, you will want to make sure that you specify the sub part of the domain in the Host/Name/Alias field for most DNS providers.

1. Enter the sub part of the domain, for example if the subdomain is mail.mxtoolbox.com you would want to enter mail into that field.

SPF and DMARC Alignment

By default, Mimecast will set you up for sending using one of their domains for the return-path address. This domain will NOT pass SPF Alignment. At this time, this provider does NOT provide any mechanism that will allow SPF Alignment to pass. You need to enable DKIM for this provider to ensure your email will pass DMARC Compliance.

How to Set Up/Modify DKIM for Mimecast

To do this, create an Outbound Signing Definition. Once this definition is produced, it will inform you what needs to be added to your DNS record. For more information on implementing DKIM for Mimecast, click here and follow the “Set Up DKIM for Mimecast” path.

As a user of this outbound email provider, Mimecast customers are afforded DKIM signing because it supports this mechanism. By utilizing its self-service portal, you can manually set up DKIM at your convenience. Overall, Mimecast provides DKIM signing and self-service set up, resulting in a streamlined process.