Is Cox purging email accounts?

On one of my user email accounts, we received an email from:

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residential@email.cox.com

FINAL NOTICE: Your Cox.Net Email Account will be Deleted

Dear Cox Email User,

We noticed that you haven't signed in to one or more of your Cox.net email accounts ********@cox.net in the past 150 days. As part of maintenance, we evaluate email activity to optimize our support systems and because you haven't signed in to check email recently, your account has been flagged as "inactive".

Unless you take action, your email account and all messages, contacts and data contained in it will be deleted on April 5, 2017. Once an account is deleted the content can no longer be recovered. If you no longer need this email account, no action is required.

If you want to keep your email account, simply sign into the Cox.net email account(s) you wish to retain before the deadline above. To access your Cox Email, type the following URL into your web browser: webmail.cox.net.
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Since all links point to cox.com or cox.net & the instructions say to manually type the webmail address into your browser, I have to assume this is legit email from Cox. When I signed on to my main account and looked at my users, yes, the subject user was marked as "inactive" but not deleted. I was able to reactive the user using a link from there.

Since when is Cox purging inactive accounts every 150 days, is there anything stating this on Cox's website? This email looks so much like phishing, I can see customers ignoring it and loosing their user accounts. Also, sending a notice only 6 days in advance (mail dated 3/30) and not copying the primary account holder is not good policy/customer service. I hope a Cox mod can clarify the policy and when it went into effect. Thanks