Altice USA, Suddenlink, Optonline, Cablevision Email Domains (2024 Update)

Cablevision, Optonline, and Suddenlink 
cable internet services all seem to be owned by Altice USA, a company spun out from the European telecommunications provider Altice.

Altice USA is a collection of brands brought together via multiple acquisitions, and Altice USA has outsourced email service for these domains to a company called Openwave. Previously, mail service for the domains was provided by an entity called Synchronoss, but that company seems to have been purchased by or spun out from its prior company and now what remains is Openwave. Alas, I wasn't able to find any email postmaster/deliverability-specific contact information for Openwave, but with this list of domains you could at least easily configure and adjust throughput and throttle settings as necessary.

Cablevision, Optonline, and Suddenlink Email Domains include:,,,,,,,,,,,,,

As of June 2024, all of the above domains have MX records that point to

Another set of domains all have an MX record pointing to "" which has the same IP address as the MX. I suspect that these are random domains for customers of Altice, and perhaps not actually Altice themselves. This may still come in handy when segmenting out Altice users and customers.

Those domains are:,,,,,,,,

Altice USA has a number of corporate domains. The mail for all of these corporate domains are hosted by Microsoft. These corporate domains include:,,,,,

Special thanks to Tam Bond for the tip on updated DNS settings for these domains!

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