Comcast blocking Gmail

This has been intermittent for months. Repeated calls to tech support with no resolution. This is business communication. The IP is a Google server in Mountain View CA.

554 resimta-c2p-559798.sys.comcast.net resimta-c2p-559798.sys.comcast.net 74.125.82.193 found on one or more DNSBLs, see https://postmaster.comcast.net/smtp-error-codes.php#BL000100