Need help discerning if a post from ATT is a scam

I received an email from [email scrubbed] saying "Our record shows that your   Mailbox is outdated due to our system upgrade to  Mail ,  AT&T Mail is deactivating all outdated mailbox versions today. Kindly update your mail account to our new version. Failure to do so will result in losing your mailbox permanently.  This will even keep your information more secure.  Please Upgrade now."

Then a link was provided. 

I think this is a scam, but need to confirm.

Thanks,

KB