Each year, we hear marketers ask the same questions: “When is the best time to send an email? How do I ensure our lands are on top before a competitor’s email pushes it down? When are users most likely to engage with our content?” 

We have years of test data to prove that “timing” matters but how/where/when is quite nuanced.  What’s clear is that before you can optimize send-time, you need to ensure delivery is successful, fast, and inboxing. Most senders are not achieving those basics to the full extent, and that needs to come first.

Email behaviours are evolving, and most users check emails multiple times per day, up to 20x per day, depending on the mailbox provider, cohort, and app/device.  ESPs like to promote their Send Time Optimization tools as a secret weapon that improves top-of-inbox placement, but they should be scrutinized, as many tools simply predict the all-encompassing “best time” per user based on a simplified set of past behaviours, reinforcing biased pattern data.  Extensive testing of these STO tools against various baseline dispatch times has not always proved beneficial; however, the situation is evolving as machine learning and AI are now improving these tools compared to years ago.

“Timing” is just one piece of a far more complex puzzle. Factors like engagement and interaction signals, list health, consent, and authentication all affect whether your email arrives, or is even inboxed and seen.  This complexity is especially critical during high-volume periods like BFMC.  Keep in mind that it’s less relevant to optimize for send-time if your emails aren’t actually landing in the inbox and getting noticed amid the flood of competing messages.

In this article, we’ll break down what really matters for BFCM send-time strategy, what works, what doesn’t, and how to balance timing with relevance, deliverability, and engagement so your emails don’t just send, they get received timely and seen.


What do we mean by “email send time strategy”?
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‍Sending strategy is not just about hitting an optimal time when users are most likely to open.  Beyond policy and authentication, it’s about doing the basics right: sending to the right mix of recipients, balancing cadence/frequency across various engagement groups, and ending relevant content within appropriate windows that respect your recipients’ local time zones and cultural norms.  An email at 11pm might be perfectly acceptable in one country, but in another, it’s probably going to sit in the inbox until the next morning.It’s also about the objectives. If your email is part of a time-sensitive promotion (flash sale, early-access, door-crasher, limited-time offer), then optimizing send time is probably not relevant because you need the message to be received at a precise moment.


The reality of email delivery
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‍When you schedule an email for a certain time, that doesn’t mean it’s delivered successfully at that time, or lands in the inbox immediately.  There are a few steps between sending and receiving, and in short, your ESP compiles the target audience, exclusions, conditions, and personalizations → queues the send → connects with the receiving mailbox provider → retries the send if not accepted, and repeats.  Each provider has rules on how many connections or messages it will accept per second, minute, or hour. If your domain or sending IP has a weak reputation, emails can be deferred, rate-limited, or even blocked outright.On top of that, real-time factors matter; complaints, invalid bounces, and low engagement can trigger ESP throttling or mailbox pushback. This means the “send time” is just the start; actual delivery can be delayed by minutes or hours, sometimes more. 

Some platforms provide delivery histogram reporting (the distribution of when emails are actually received). Some ESPs provide “throttle” limits on how many emails can be delivered per hour, so be sure to check if this affects you. 


The reality of BFCM traffic + Inbox Crowding

As Q4 volumes ramp up, mailbox providers experience increased stress on infrastructure due to the sheer volume of inbound emails. It’s also a time when abuse and spammy sending behaviour peaks, requiring tightened filters to protect end-users. 

Mailbox-providers can delay/defer/throttle incoming mail, particularly from senders or IP-ranges with lower reputations, or sharp deviations in sending patterns and recipient interaction behaviour.  This means you can’t always assume a scheduled email at 9:00am will arrive or inbox at that time.

To mitigate the risk of delays, it often makes sense to start sending earlier – the question is how much earlier? That needs to be monitored and tested to understand how much time is needed to process and deliver your messages successfully during peak time.  Every email has timestamps for send vs. delivered, bounced, opened, clicked, etc. - so use that data to evaluate when users are receiving and interacting, and adjust your send times as needed.

During higher volume BFCM weeks, giving your emails enough runway to be accepted and delivered safely is often more important than narrowly targeting a specific send time.  And here’s where the old timing obsession really gets challenged: your audience’s inbox is busier than ever.

If your goal is to be the first email a user sees, remember you’re competing with dozens of other senders hitting the same window. Even if you technically land first, how long can you stay at the top before their mailbox is flooded and other messages push yours down?

Some brands find it too much to evaluate, and will simply revert to an “earlier is better” approach.  For example, consider a subscriber who checks emails on their phone whilst riding the subway to work at 8:30 am each morning – would they miss an email sent at 10 am or 2 pm, until the next morning?  The idea is that an email sent earlier (let’s say 7:50 am) would be more likely to be seen by all subscribers, irrespective of their engagement patterns throughout the day, because the mailing was delivered and waiting.


The Mailbox-Provider Gatekeeper

When an email is sent may differ from when an email is accepted/delivered.  There are different steps an email takes to get to the end recipients.  For example, a large segment with complex conditional logic could take many minutes to process and pre-compile before it can be queued in the sending MTA.  Once in transit, the receiving server may have limits on the connections, retry rates, or volume that can be accepted per second/minute/hour per sending IP address or domain.

Not all emails are delivered on the first send attempt, and could bounce transiently over and over until it’s either accepted or the maximum number of retries is exceeded.  This sometimes depends on the technical infrastructure and capacity of the receiving server to access/process the email at their inbound gateway.

Your sending IP and domain reputation also matter because brands with “poor reputation” may experience push-back, rate-limiting delays, and deferrals - which means it could take minutes, hours, or even days to deliver successfully - in other cases, this email might be rejected dynamically for a certain time, or until the next campaign sendout. This means brands need to consider how much they are sending, where they are sending, and measure the delivery (distribution histogram) of how quickly emails are being received relative to when they are being sent. Unfortunately, not all ESP platforms provide such insights beyond the send time.

In recent news, Gmail announced the Promotion Tab will now sort emails according to relevance - which is largely driven by engagement and interaction signals. This moves users away from the traditional "Most Recent" chronological view that we’ve been used to.  Gmail also highlights “Top deals for you” and “nudges” time-sensitive content. This is significant because your audience is more likely to see emails from brands they regularly engage with, and less likely to see messages from low-engagement senders, even if you hit the traditional “perfect time.”

This means being relevant to your subscribers and maintaining strong long-term engagement becomes the driving factor to improve visibility, not just who is first or landing their emails at the right time. For marketers, that shifts the focus from chasing the “best time” to investing in content, list health, and engagement over the long-term.


When Does Send Time Matter?

‍Send time still matters, but context is key. Timing matters when your audience is in a predictable pattern, when sending non-urgent content like newsletters and lifecycle messages, or when sending time-sensitive behavior-triggered. That means aligning send windows with recipient habits to boost response behaviour – but it doesn’t always mean using STO tools.Precise delivery time matters when messages are urgent or highly time-sensitive, like flash sales and limited offers. Using send-time optimization on BFCM campaigns could potentially hurt performance if it means skipping profiles or delaying the message for some recipients.

Event and behavioural triggered emails like Abandoned Cart require a lot of send-time testing, which is less about the time-of-day, and more about the time-since-event optimization.  The key here is testing different intervals and measuring success not just by opens, but by recovery rates and conversions. Factors like cohort behaviour, purchase history, cart value, etc. can influence what timing cadence works best.  Waiting too long risks losing the shopper’s interest, while sending too soon can feel intrusive. These revenue-driver emails should be regularly tested to optimize balanced urgency, relevance, and user experience.

Time-sensitive and business-critical triggers like DOI confirmation, welcome, password reset, order, payment, and shipment notifications should ideally be delivered and inboxed within seconds. If it takes minutes or hours to receive, that’s going to negatively affect the user-experience, and even drive-up internal costs; eg. customer service costs due to inbound calls/tickets) or revenue loss due to poor experience, churn, cancellation, etc..


Practical Tips to Consider:

Whether or not time sensitivity is a factor, get your revenue-drivers + engaged-user emails out-the-door and delivered first, and worry about delivery to low-value cohorts later.

This time of year, senders dig into dusty corners of their lists to find audiences for winback and re-engagement. Those audiences can often be large, dormant, and risky.  There is nothing worse than bogging-down email delivery and risking delays and spam-filtering because you sent to a massive risky audience with a high ratio of disengaged users. Even worse if that audience contains users who shouldn’t receive emails, complains, and/or contains a high rate of invalid or expired addresses. 

Avoid sending at predictable peak traffic times (eg. 10am) – for example, you might instead try testing the dispatch at 9:47am instead.

Avoid sending everything all at once – some platforms allow you to “spread” a dispatch over multiple hours or days, but that doesn’t do much to distribute the risk, or learn from the cohorts.

Brands often care about who will convert, but mailbox-providers care about email opt-in consent, authentication, email engagement signals, spam-complaints, list quality, etc.  So when expanding audience reach (e.g. inactives, unengaged, winback, re-engagement), carefully review who qualifies and who doesn’t – and score the audience using a risk matrix.

Consider the engagement ratio across the audience, since engaged audiences can be affected and filtered in real-time due to the impact of disengaged audiences.  Structure your dispatch strategy according to engagement and cohorts – and get those emails sent and delivered first, they drive revenue and could be expecting your emails. 

Consider scheduling less-engaged audiences in a separate dispatch some minutes or even hours later.  Also consider how frequently you’ll email various user cohorts across the engagement spectrum. You’re more likely to experience spam-filtering and rate-limiting delays if you are treating all users equally, and over-communicating to disengaged users, or under communicating to engaged users. 

We recommend sub-segmenting questionable audiences into smaller groups: (i) to learn how different users react to content/offers, and (ii) to create a low-ratio blend-effect, mitigating the risk and impact of ‘dilution’. 

For example, if your typical daily target audience is 100k, and you want to mail an additional 200k dormant users… you could risk sending all at once (increasing the disengagement ratio by 66.67%) -OR- you could first send a sample-size to measure the response metrics, and then proceed to send ~10% (20k of the 200k) over the next 10 campaigns, until the dormant audience list is exhausted. That increases the disengagement ratio by ~16.67% which is a safer ratio. 

A more practical approach is to sub-segment the group in question according to most-likely and least-likely to engage, based on available historical behaviours.  There may be some users who should receive more emails, and there may be others who shouldn’t receive at all.  Each sub-segment may have a different reaction rate, and that may determine how often they receive subsequent emails.


Summary:

Send-time is a tool and tactic, not a strategy. Focus first on fundamentals like strong deliverability, clean lists, delivering relevant and engaging content, opt-in consent, managing user-expectations, understanding touch-points and frictions.  Your first objective is to get emails delivered quickly, without delays, and to the inbox.

Layer-in timing strategies where they actually make a difference – for non-urgent campaigns, segmented behavioral sends, and lifecycle messaging. Shift your perspective from “getting emails sent” to “what impact will sending this have on my deliverability”.

‍During high-volume periods like BFCM, think about what other senders are doing, and how mailbox-providers are likely to react to your audiences and sending practices.

Even when timing is relevant, it’s just one part of a bigger puzzle; delivery infrastructure, IP/domain reputation, list hygiene, content relevance, and engagement all play a bigger role than the exact minute you hit “send.”