u/sendpost95

We run an ecommerce email program and occasionally have flash sales where we need to send 3-4x our normal daily volume in a single blast. Every time we do this our deliverability tanks for days after. Anyone found a good way to handle volume spikes without wrecking your sender reputation?

We tried warming up the volume gradually the day before by sending a smaller campaign first. Helped a little but not enough. We also cleaned the list before every flash sale so were only hitting engaged contacts. Made the numbers look better on paper but the deliverability dip still happened.

Our ESP doesnt give us any control over sending speed per provider. It just blasts everything out as fast as it can. Starting to wonder if thats the actual problem but not sure what I can even do about it from my end.

We've been running our own sending infrastructure for a few years now. If I could go back and tell first-year me one thing it would be: get your SPF setup right on day one. Everything else you can fix later. This one gets exponentially harder.

Most ESPs start by having customers add CIDR ranges directly into their SPF records. Works fine at 10-20 customers. Then you scale and things start breaking in two ways.

The security gap

Your IP ranges grow, you add broader CIDR blocks. If a spammer has an IP in that same range, they can pass SPF checks on your customers domain. Not great.

The operational nightmare (this is the real killer)

SPF has a hard limit of 10 DNS lookups. Sounds like plenty. Its not.

Take a customer on xyz.com sending through Google Workspace, HubSpot, and your ESP. Thats three SPF includes. But:

→ spf.google.com alone resolves to spf1, spf2, spf3.google.com, each pointing to different CIDR ranges. Thats 4 lookups from one entry.

HubSpot adds more. By the time they add your record theyre at 9 or 10 lookups

Now you need to change your infra. Swap IPs, restructure CIDR ranges, whatever.

Every customer has to update their DNS. And if your change breaks their SPF record youre not just breaking email from your ESP. Youre breaking their Google Workspace. Their HubSpot campaigns. Everything. And they wont know why until their CEOs emails start bouncing.

Multiply that by hundreds of customers each with different DNS setups. Its months of coordination for what should be a routine infra change.

What we ended up doing was return path CNAME mapping. Customers point a CNAME to us, we manage SPF behind it. We can swap our entire infrastructure without a single customer touching their DNS.

Not a novel approach, plenty of mature senders do this. But the number of ESPs ive talked to who started with direct SPF and are now stuck is wild.

We've been running our own sending infrastructure for a few years now. If I could go back and tell first-year me one thing it would be: get your SPF setup right on day one. Everything else you can fix later. This one gets exponentially harder.

Most ESPs start by having customers add CIDR ranges directly into their SPF records. Works fine at 10-20 customers. Then you scale and things start breaking in two ways.

The security gap

Your IP ranges grow, you add broader CIDR blocks. If a spammer has an IP in that same range, they can pass SPF checks on your customers domain. Not great.

The operational nightmare (this is the real killer)

SPF has a hard limit of 10 DNS lookups. Sounds like plenty. Its not.

Take a customer on xyz.com sending through Google Workspace, HubSpot, and your ESP. Thats three SPF includes. But:

→ spf.google.com alone resolves to spf1, spf2, spf3.google.com, each pointing to different CIDR ranges. Thats 4 lookups from one entry.

HubSpot adds more. By the time they add your record theyre at 9 or 10 lookups

Now you need to change your infra. Swap IPs, restructure CIDR ranges, whatever.

Every customer has to update their DNS. And if your change breaks their SPF record youre not just breaking email from your ESP. Youre breaking their Google Workspace. Their HubSpot campaigns. Everything. And they wont know why until their CEOs emails start bouncing.

Multiply that by hundreds of customers each with different DNS setups. Its months of coordination for what should be a routine infra change.

What we ended up doing was return path CNAME mapping. Customers point a CNAME to us, we manage SPF behind it. We can swap our entire infrastructure without a single customer touching their DNS.

Not a novel approach, plenty of mature senders do this. But the number of ESPs ive talked to who started with direct SPF and are now stuck is wild.