Frequently Asked Question

Ensuring Email Deliverability through our email gateways
Last Updated a year ago

Our email gateways have enhanced antivirus and antispam protection which uses a catalogue of methods to detect and prevent spam and malicious email's. We sometimes are asked by our customers to investigate why a particular sender cannot email them, a question which we can rarely answer since it would be like asking the post office why you didn't receive a letter. Senders who are having issues sending to our customers must contact their mail providers to investigate.

There are some guidelines however which may assist those mail providers in diagnosing the issue, some are mandatory, some optional, and some just best practice. Ensuring compliance with these doesn't guarantee delivery but it helps.

RFC Compliance

Your mail service, the one which is the last in the path before it connects with us must be RFC Compliant. By this we mean it must follow the established standards for both its communications and its host configuration. There are a number of RFC's involved and professional mail service providers are familiar with them.


DKim is a method by which email can be 'signed' by a server, its actually not that fantastic and can be compromised but if you provide it, it must be correct. If a corresponding DMARK record exists then this must also be correct. Just having DKIM and DMARK doesn't improve your changes of delivery, as some would suggest but if its there, it must be correct.


SPF is a DNS record which defines the IP addresses of servers allowed to send mail on your behalf. That doesn't mean its foolproof but its a good basic step. If you have an SPF record then it must be correct, and must list the IP's of the server connecting with us.


Whatever email address you send from, MUST also accept email. If you're sending from an email address that doesn't exist, is not setup, is setup but is not accepting email, then your email will likely be rejected. Return paths are a requirement, and we use them to validate the email address.


Not all attachments are accepted, but most are as long as they can be successfully scanned. Encrypted files that cannot be scanned will sometimes be passed if other metrics are ok but there's no guarantee. Most offending attachments are just stripped from the email, but in some cases the entire email could be excluded.


There are a number of organisations that maintain a blacklist of server's which are known to be originating spam. These blacklists are updated regularly and our systems consult them before accepting email. If you're mail services provider is listed then in most cases email will be rejected, and it is for them to resolve this with the blacklists directly.


For mail service providers who are often on blacklists, reputation provides an overview of a mail service provdiers response to spam, and their commitment to reducing it. Mail service providers who are not currently blacklisted, but who have a poor reputation can find themselves blocked. Reputation is not something that can be instantly repaired.

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