Adding IP addresses of 3rd-party SMTP gateway (MailChannels)

[Quinn Comendant <quinn@xxxxxxxxxxxxxxx>]

We use mailchannels.com for delivery of mail for all domains on our network. I tried to add their IP addresses to my DNSWL ID (25870), but some failed because (I think) they belong to the DNSWL ID of MailChannels. Their IPs are (from their SPF):

103.18.109.138/32
172.255.62.10/32
172.255.62.11/32
177.153.0.128/25
177.153.0.130/32
191.252.57.0/25
199.10.31.235/32
199.10.31.236/32
23.83.208.1/20
46.232.183.0/24
54.214.232.113/32

According to your Policy page, "If it can be shown that an IP address in “foreign” IP space is dedicated to the entity (eg an outsourced mailserver), this counts as “controlling their own IP address”." — this appears to be true in this case: MailChannels is our outsourced mailserver provider. 

How can I add these IP addresses to my domain's whitelist?

Thanks,
Quinn