SMTP support on InterServer instances

TLDR: Any one dealing in SMTP is aware of abuse and spam, and aware that SPAM can lead to ip blacklisting at collateral damage. It should come as no surprise that SMTP is blocked by default and requires additional verification.

     InterServer blocks outbound traffic on port 25 (SMTP) on all VPS and dedicated servers by default following generally accepted standards at https://www.m3aawg.org/sites/default/files/doc_files/managing_port_25_2023.pdf. Once a system has been with active for a month, and has no outstanding invoices, you can create a request to unblock these ports for a valid use case by providing:

* A statement outlining your plan for assuring that your account isn’t implicated in sending unwanted emails.
* Setting a server hostname pointing to the main IP of your vps instance and a valid reverse dns.
* Expectations: Awareness of how to set proper SPF, knowledge of DKIM/DMARC, forward and reverse dns settings and how to make the required dns changes. Users who do not are encouraged to get a managed vps, or shared hosting.

     Please be aware: Systems which are for mailing only are disallowed on InterServer’s network – a system who’s primary purpose is sending email over SMTP. To be more clear, this does not target standard webhosting companies but specifically if for those who are trying to create a server just for email, sending out on all ips. The definition is to be more clear on what is allowed, and not allowed. This means, a server, that gets spam complaints from multiple ips would be suspect. Interserver’s network is monitored through multiple feedback loops and may suspend or re-block smtp on a system that has a high complaint ratio. Running a single opt-in, opt-out only, or any other non-double opt-in mailing list may result in suspension.

     IP rotation for sending email is not permitted with our prior authorization. For example: A single server with 5 ips: During standard monitoring if these 5 ips show as getting spam complaints or hitting traps such as at hotmail SNDS program, smtp will be blocked unless prior authorization has done even if an smtp request has been approved. As a general rule ip rotation is not permitted however exceptions will be made to known web-hosting companies running a mail server, members of M3AAG, known large mailing lists or servers that have been verified, and known mailing services. To be simple: A well known company or postmaster who is known to run a good mail server will not have issues getting port 25 opened.

Requests could be denied based on domain age, reputation, and a request must be made per each system meeting the above requirements.

Requests coming from free email accounts may be denied, or require further details to open the smtp service.

Cases of systems migrating who need SMTP immediately may include that in their initial request.

Once smtp is approved please review steps to take when starting a mail server. Please be aware SMTP access may be closed for failure to respond to spam complaints, or ip reputation damage especially with in the first 30 day window of opening SMTP. For example an obvious cold or non double opt in mailing on a single domain system may be blocked with out warning. Factors will be taken into account like shared hosting and webhosting servers of course. Generally speaking it is easy to tell based on complaints what is pure spam vs a compromised account needing to be cleaned up.