Several Email Service Providers, Bulk Email Senders, and Email Inbox Providers are offering a new type of service that promises to get your emails in front of your recipients at the top of the inbox and therefore increase your open and click-through rates. Does Send Time Optimization affect your email deliverability?
What Is Send Time Optimization (STO)?
Send Time Optimization, and a similar technology called View Time Optimization, uses artificial intelligence to analyze your email recipients email opening habits and times your emails to arrive just before the user would view or open their email box. The general pitch is that being the top email or first email a user sees improves the open rate and better open rates yields better click-through rates and purchases.
Does it work?
STO is attempting to predict when a customer will actually check email and open the emails in their inbox, while VTO is provider side technology to delay email delivery until the moment the inbox is checked. Marketing claims for STO/VTO range from improving open rates by 2% to 4x and click-through rates by 2% to 2x Note, improving open rates by 4x is ludicrous if your open rates are near the industry average 21%, so beware of what you are buying into. However, it seems reasonable that being top of the inbox would invoke a improved email metrics, especially in use cases that are geared toward re-engaging with a past customer.
Is STO Worth the Cost?
That really depends on your existing email delivery management posture. There are many options that can dramatically improve your email deliverability and therefore your open rates for less, and some techniques your should be doing before enlisting in an optimization service. Here are a few of our recommendations:
- Slow your roll – Reduce the number of emails you send to your customers. Consumer email fatigue is a real thing that creates passive unsubscribe behavior, reducing your open and click-through rates. One company realized that four different product marketers were sending a weekly email blast about six different products all targeting senior executives. Combined with weekly newsletters and nurturing campaigns, webinar requests, etc. these prospects were massively turned off to the marketing message before they even read it. Open rates will suffer if you stuff the inbox so reducing the number of times you email someone is in your best interest.
- Clean out your rolodex – Okay, really, clean up your contact lists. If someone has not opened an email in six months, unsubscribe them! They aEre no longer interested. Continuing to send to an out of date contact obscures what your real open rates really are.
- Improve your content – Too often email marketers are inside-out, focusing on their product or solution without regard to the actual user or buyer. Your email marketing content should be outside-in: engaging and interesting enough for your users to open, read, and examine your offer. Also, it’s time to evaluate your subject lines, are they gimmicky and spammy? You could be turning off your audience, even if the email isn’t blocked as spam.
- AB Test your pitches – Relying on old, out-of-date pitches can lower your open rates over time. Periodically AB testing new pitches forces you to reevaluate your marketing and may give new life to existing prospects, increasing open rates and click-throughs.
- Improve your Email Deliverability Posture – Adopting new technologies like SPF, DKIM and DMARC can dramatically improve email open rates by increasing the amount of your email that actually makes it to the inbox. A recent MxToolbox customer saw a 2% rise in open rates in the first few months just by improving DMARC compliance.

MxToolbox Delivery Center allows you to peer beneath the surface of the iceberg and see the the hidden issues affecting your email delivery – Blacklisting, SPF Failures, missing DKIM signatures, low DMARC compliance, etc. Only with a tool like Delivery Center can you really understand and manage your email deliverability.
Our Recommendation
STO is a valuable technology, but works best when your email deliverability is already at its best. The more you can do to improve your delivery rates before taking advantage of STO, the more value STO will have for you.