I rolled my own lifecycle emails to skip Customer.io. The branching took a weekend. The plumbing quietly ate two months. Here is the honest build versus buy story, from having built it.
Every small SaaS founder hits this fork. You want to send emails based on what people actually do in your product, not blast the same drip to everyone. You look at the tools built for it, Customer.io and the rest, and they are genuinely good. They are also priced for companies further along than you, and a few have no free tier at all. So you do the rational thing. You decide to build it yourself. How hard can it be.
The branching is not hard. That part really is a weekend. The plumbing underneath is what nobody warns you about, and it is where the time and money you thought you saved quietly disappears.
The easy 80 percent.
The logic everyone pictures when they say behavior based email is the simple bit. Fire an event, check a condition, send or do not send. If they finished setup, send the next step. If they did not, send the nudge. Branch on plan tier. Wait two days. You can sketch this on a napkin and have a basic version running over a weekend with a cron job, an events table, and your email provider.
If that were the whole job, nobody would pay for a tool. The reason these tools exist is everything that sits under that napkin sketch.
The 20 percent that ate the months.
None of these are features you finish. They are infrastructure you maintain. That cron job and events table you started with slowly turns into a small data platform you did not set out to build, running in the background, eating the hours you wanted to spend on your actual product.
1. Identity stitching.
A person clicks around anonymously, signs up, logs in on their phone, gets invited to a teammate workspace. That is one human across four sessions and two devices. If your events do not all resolve to one profile, your did they finish setup check is wrong, and you email people about things they already did. Getting anonymous to identified merging right, and keeping it right, is real infrastructure, not a column in a table.
2. The wait versus convert race.
You queue the you have not done X yet email, the user does X thirty seconds later, and it still goes out because the check ran before the send, not at it. Any single point in time check is stale by the time the message lands. Fixing it properly means the goal event has to actively pull someone out of an in flight sequence and cancel a queued send, which is harder than checking a condition at each step.
3. Frequency capping across flows.
Your onboarding sequence and your feature nudge both decide today is a good day to email the same person. Per flow logic cannot see that. You need a cap that spans every automation at once, or you train your best users to ignore you and your deliverability slowly rots.
4. Event ingestion lag and idempotency.
Events arrive late, out of order, and sometimes twice. The same signup fires three times on a flaky network. If your pipeline is not idempotent and ordering aware, you double send, you misfire, and you cannot trust your own triggers. Dedup and ordering are unglamorous and absolutely load bearing.
5. Suppression and exits.
Unsubscribes, hard bounces, churned accounts, people already in the end state you are pushing them toward. Every one of those is a reason to not send, and each is a branch you have to remember to build and maintain. The hard part of lifecycle email is not sending. It is reliably deciding when not to.
6. Deliverability.
SPF, DKIM, DMARC, warmup, reputation, and the fact that a few bad sends to the wrong people quietly degrade inbox placement for the mail that actually matters, like receipts and password resets.
So is building it wrong?
No. If you genuinely enjoy this layer, or you have very specific needs, or you have the time, rolling your own is a legitimate choice and you will learn a lot. The mistake is not building it. The mistake is assuming it is a weekend project and discovering two months later that you accidentally became the maintainer of an email pipeline.
The honest build versus buy test is simple. If the branching is the whole job for you, build it. If you find yourself reinventing identity resolution, dedup, frequency caps, and exit races, you are rebuilding a tool, and you should ask whether that is the best use of the only resource you cannot get back, which is your time before revenue. It is the same logic behind running lifecycle email without a developer and behind choosing event triggered over time based emails : spend effort where it changes outcomes, not on plumbing.
The in between that did not exist.
I went down the build path, hit every one of these, and that is what made me build GetFluxly: behavior triggered lifecycle email with the plumbing already handled, without the Customer.io price wall, and a 14 day trial to start, no card required. You bring the email use. It does not replace a whole marketing stack. It handles the part that quietly eats your weekends. If you want the bigger picture, the lifecycle email automation guide covers the full loop, and the pricing page shows how the trial and plans break down.
If you are at that fork right now, at least go in with your eyes open about the 20 percent. That is the part that decides whether do it yourself actually saves you anything.
Build vs buy, answered.
Should I build my own lifecycle emails or buy a tool?
If the branching is genuinely the whole job for you, build it, it is a weekend. If you find yourself reinventing identity resolution, event dedup, frequency caps, and exit races, you are rebuilding a tool, and your time before revenue is usually better spent elsewhere.
What is the hardest part of building lifecycle email yourself?
Not the sending and not the branching. It is the plumbing underneath: stitching anonymous activity to the real user, deduping events that arrive late or twice, capping frequency across flows, and the suppression and exit logic that decides when not to send.
Is Customer.io worth it for an early stage SaaS?
Customer.io is genuinely good, but it is priced for teams further along and has no free tier. For a pre revenue or just launched founder that is a real barrier, which is exactly why so many early teams try to build their own instead.
Can I start behavior triggered email for free?
Yes. GetFluxly gives you a 14 day trial, no card required, then it is one plan at $29 a month flat, and you plug in the email provider you already use, so you can trigger lifecycle email off product events without the price wall and without building the pipeline yourself.