ℹ️ What's this article about?
SMS messages can be blocked or filtered before they ever reach your patient's phone — and you won't always know it's happened. This article explains how carrier spam filters work, what triggers them, and the simple steps you can take to make sure your SMS messages land in the right place.
Sending an SMS from Peptalkr doesn't guarantee it arrives. Mobile carriers (the networks that deliver your messages) run sophisticated spam filtering systems that scan every message before it's delivered. If your message looks suspicious, it gets blocked. No notification, no bounce, just silence.
The good news is that most filtering is avoidable. Following a few straightforward best practices means your messages reach patients reliably - whether you're sending appointment reminders, one-off campaigns, or anything in between.
Write SMS messages that pass spam filters
Spam filters analyse your message content and look for patterns associated with unwanted or fraudulent messaging. The same things that make a message feel spammy to a person also trigger filters.
✅ Do:
Clearly identify your clinic by name early in the message
Keep your message concise and to the point
Use plain, natural language as if you were writing to a real person
Include only one link if you need to link somewhere, and make it to your own website (more about branded links here)
Write in sentence case with normal capitalisation
Example of a good SMS:
Hi Jennifer, we have some availability open up for this week at Pepper's Practice. You can book yourself in easily here: yourclinic.com/book
❌ Don't:
Use ALL CAPS or excessive exclamation marks!!!
Include phrases like "FREE", "CLICK HERE", "ACT NOW", "URGENT", or "LIMITED TIME"
Stack multiple links in a single message
Use public URL shorteners like bit.ly or tinyurl.com - these are heavily associated with spam and phishing. Link directly to your website or booking page instead, or swap to branded links.
Use excessive special characters
Send a message that reads like an advertisement with no personal context
Example of a bad SMS:
Hi Jennifer! FREE appointment slots have just opened up — CLICK HERE to book: bit.ly/abc123
Only send to people who want to hear from you
Carrier filters pay close attention to how recipients respond to your messages. High opt-out rates and spam complaints are major red flags that will get your messages filtered - and your sender number flagged.
Peptalkr only allows you to send SMS to patients in your Cliniko database. For messages marked as marketing in Peptalkr, your patients' marketing consent status is inherited from Cliniko - so you should always ensure Cliniko reflects accurate, up-to-date consent before sending.
For non-marketing messages (such as appointment reminders or clinical communications), you must ensure you're sending only to people who it's appropriate and lawful to contact. Non-marketing SMS must comply with the messaging rules in your region.
All marketing SMS sent from Peptalkr automatically include an opt-out link. Do not attempt to remove this by sending a non-marketing message - it's there to protect both your patients and your sender reputation.
⚠️ Warning
If a patient opts out and continues to receive marketing messages, carriers will flag your number as a spam sender. This can affect delivery for all your SMS, not just to that patient. Always keep your Cliniko consent data up to date.
Be thoughtful about timing and frequency
Sending too many messages, or messages at the wrong time, increases the chance patients will report them as spam — which damages your sender reputation.
Don't send outside reasonable hours. Aim to send between 9am and 8pm in your patients' local time zone. Messages that arrive in the middle of the night are far more likely to get reported.
Don't over-send. For marketing SMS in particular, less is more. Patients who feel bombarded will opt out or report your messages. For one-off campaigns, consider how recently you last contacted the same group.
For appointment-based SMS (reminders, confirmations), timing is usually handled by your automation settings — just make sure they're configured sensibly.
Using links in SMS
Links are one of the biggest triggers for spam filters, so how you use them matters.
Use links to your own domain wherever possible. If the link clearly comes from your clinic (e.g. yourclinic.com/book), filters — and patients — trust it far more than a generic shortened URL.
Avoid public URL shorteners (bit.ly, tinyurl, ow.ly etc). These services are heavily abused by spammers and are routinely flagged by carrier filters.
Only include one link per message. Multiple links in a single SMS is a strong spam signal.
Make sure any link you send is live and working. Broken links frustrate patients and reflect poorly on your clinic.
💡 Tip : If you want to shorten your links, check out this article.
What happens if your messages get filtered
If a carrier blocks your messages, Peptalkr only finds out after they've already been sent. Because the message reached the carrier network before being blocked, the cost is still charged — to us, and then to you via your SMS credits. There is currently no way to automatically stop a send mid-way if blocking is detected.
This is why following best practices before you send is so important — prevention is the only reliable protection.
Test before you send to a large group
For any marketing SMS blast, we strongly recommend sending to a very small group first to confirm everything is working as expected before rolling it out more widely.
Option 1 — Send to yourself first
Create a dummy patient file in Cliniko using your own mobile number, and add a medical alert called something like "SMS-test". When building your blast, filter by that medical alert so only your dummy patient is included. If the message arrives on your phone, you know it's delivering correctly. Your dummy patient will still need a recent appointment as all SMS blasts require you to set an appointment date range within which the recipient must have attended an appointment. So go ahead and book an appointment in the past so you can receive the SMS.
Option 2 — Start with a tiny audience
Before sending to your full patient list, narrow your filters significantly — for example, set your appointment date range to cover just one or two days. Aim for fewer than 10 recipients. Check that those messages deliver successfully, then expand your filters and send to the wider group.
💡 Tip: Both options can be combined. Send to yourself first, then to a small group, then to everyone. A few minutes of testing can save you from spending SMS credits on a blast that never reached anyone.
FAQs
Do I need to include an opt-out option?
Do I need to include an opt-out option?
For any SMS marked as marketing in Peptalkr, an opt-out link is automatically included — you don't need to add one manually. For non-marketing messages, you should still ensure you're only messaging people it's appropriate to contact.
What is a spam filter and how does it work?
What is a spam filter and how does it work?
Mobile carriers (like Optus, Vodafone, O2, Spark etc) run automated systems that scan every SMS message before it's delivered. These systems look at message content, volume patterns, link types, and recipient complaint rates to decide whether a message is legitimate or unwanted. If a message looks suspicious, it gets blocked — often without any notification to the sender. These systems are continuously updated and their exact rules are not made public.
My message content looks fine — why was it still filtered?
My message content looks fine — why was it still filtered?
Filtering can also be triggered by things beyond your message content, including: a high opt-out rate from previous sends, complaints lodged by recipients, or sending a large volume of similar messages in a short period. If you're regularly experiencing filtering issues despite following best practices, contact Peptalkr support.
Does it cost anything if my message gets filtered?
Does it cost anything if my message gets filtered?
Yes. SMS charges apply when the message is sent to the carrier network, regardless of whether it's ultimately delivered to the recipient.
Can't I just use the test button to check if my message will be blocked?
Can't I just use the test button to check if my message will be blocked?
Not quite. The test send function is useful for previewing how your message looks, but it doesn't fully replicate how a real SMS is sent to a patient - so it won't tell you whether a carrier would block it. That's why we recommend the dummy patient method instead: create a patient file in Cliniko with your own mobile number and some appointment history, then send to them using a medical alert filter. Because this goes through the same process as a real patient SMS, it's a genuine test of whether your message will deliver.