Tech Support
Joined: 25 Aug 2003
Posts: 4381
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 Posted: Thu Feb 20, 2025 10:33 am Post subject: Addressing Email to SMS Delivery Issues |
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Cell phone carriers in the US have greatly tightened the volumetric and anti-spam restrictions on their public email-to-SMS gateways. Once a site sends a certain volume of traffic, carrier hosts will begin issuing rejection notices that the sender isn’t allowed to pass traffic through for a period of time. Some carriers do this in the protocol negotiation, some issue after-action notices (traditional mailer daemon bouncebacks). In addition, these restrictions are not always static, and change without any notice or notification.
How much traffic is allowed through can be directly impacted by your email domain's DMARC, SPF, A, MX and other DNS records. If there are any outstanding TXT DNS record issues with the email domain, it greatly decreases the overall volume of traffic carriers are willing to accept from the sender.
In general, email-to-SMS can no longer be considered a stable or viable method of delivery for CRITICAL messaging traffic, and it is recommended that public safety and medical industry organizations avoid using email-to-SMS as a primary delivery method.
At best, it should be treated as an implementory protocol to help a site get their messaging off the ground in the immediacy and then long-term messaging should route through a different source. Related to that, we should also talk about how SMS can be sent and there are four categories of option:
1) Email-to-SMS
This is your traditional @vtext.com for Verizon, @txt.att.net for AT&T, etc. email to SMS traffic and while this method of delivery used to be remarkably stable for quite a long time, the carriers have very deliberately made it not so by restricting the quantity and rate of traffic allowed to a point where PSAPs need more than they can provide in many cases.
2) Carrier Enterprise System
Most carriers are willing to give dispatch centers, PSAPs and other emergency management entities free access to their enterprise messaging platforms and PageGate absolutely supports the necessary communication protocols to support them.
Where possible, we recommend that these gateways be used in a public safety context, as they can offer a very reliable method of delivery with no cost to the dispatch center. The only down side is that a registration processes with the carriers is required, to have access to this option.
3) SMS API
SMS APIs are companies like Twilio, RingCentral, ClickSend, etc. that provide a messaging API and typically charge a nominal per message fee to route traffic through their gateways. When a client registers an account with one of those companies, they will have access to the necessary API keys to configure PageGate for this delivery method.
4) Cellular Hardware
On the hardware side of things, there are cellular modems/routers/gateways. These devices have an interface PageGate can use to send and receive SMS messages, just like a cell phone.
Cellular modems are easier to use with physical systems as they connect via USB or RS-232 serial connections. Cellular routers/gateways are easier to use in virtual environments as they can be reached via TCP using Telnet or SSH protocols.
PageGate is completely hardware agnostic, so a client could use Cradlepoint, Cisco, Multitech, MicroHard or any other manufacturer's hardware as long as they support RS-232, USB, Telnet or SSH connections, and have a commandset that supports sending and receiving SMS.
If you would like to set up a time to review what your site’s best option might be, please reach out! We’re happy to put you on our schedule. |
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