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[Resources] Email Deliverability

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At INBOUND19, HubSpot SVP of Product, Christopher O'Donnel announced HubSpot's current email deliverability rate is over 98%.


BOOM! Now that's serious deliverability.
- see [VIDEO] INBOUND19: HubSpot Product Spotlight | Christopher O'Donnell



A few resources that may help make sense of the many factors affecting email deliverability.



[VIDEO] HubSpot Email Health and Deliverability, September 25 2019

It's a Bird, It's a Plane, It's Email Deliverability by Courtney Sembler of HubSpot Academy (5 min Read)

Understanding Email Deliverability -- Community Articles

Understanding Email Deliverability -- Knowledge Base

Sendability issues... Hubspot send IP is blacklisted (HC Post updated 2019)
Emails getting cut off in Gmail [Message clipped] (HC Post updated 2019)

Create and send marketing emails -- Knowledge Base



Good To Know
Email Bounces and how they affect contact eligibility

How can I improve the deliverability of my emails?

Also Useful
Everything Email Marketers Need to Know About Sender Score


email-deliverability-sender-score-cta-600x197-v01.pngClick to Register


The following big dogs are responsible for sending / testing over 25% of the world's non-spam email, so should probably consider anything on their radar a priority concern.


- see 15 Email Deliverability Best Practices for Gmail (SparkPost)
- see Make It to the Inbox—Not the Spam Folder—with Litmus Spam Testing (Litmus)
- see Top Tips to Avoid Spam Filters When Sending Emails (SendGrid)
- see How to Avoid Spam Filters (MailChimp)
- see A Marketer's Guide to Email Deliverability: How to Avoid Email Spam Filters (HubSpot)

As a side note, SparkPost also has some excellent information about ramping up sends to large lists (>1M contacts) and warming up sends to lists in general. Just excellent stuff every email marketer should indelibly impress in their brains. Smiley Happy




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Gestor de la comunidad

Thanks for sharing @MFrankJohnson!

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Gestor de la comunidad

Thanks for sharing @MFrankJohnson!

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Colaborador ocasional

Thank you for a couple of great links. I have a concern regarding deliverabilty and warm-up which I would appreciate your (or anyones) view on.

We are in a discussion with a potential client (about 300 000 contacts) and today they are sending a total of about 5 million emails yearly. About 20% of those are sent more or less on a schedule not changing from one week to another.These are more transactional by nature. The rest of the emails, roughly 4 million, have a more irregular pattern where they send an email to 50 000 one week and the next they need to send an email to all 300 000 contacts within 48 hours.

How would you do this in terms of warm up and perhaps cool down? Would you need to warm up again if you haven't sent anything, or less than 300k, in say 2-3 weeks?

Superestrella de la comunidad


marketing-email-necromantic-sorcery-cover-500x667-c60.jpgUnless the list is super uber niche (to the extreme) [with emphasis], we've never heard an effective rationale for sending the exact same marketing email to 100% of any contact list. That is, unless of course we're trying to kill our contacts, then convert them. Guess that's just the segmentation junkie in us. Guiño

The conversation around transactional email is separate from the conversation around marketing email. Sure, creative minds stll find ways to capitalize on the convergence of the two. However, the goals of transactional emails and marketing emails are divergent by nature -- each with their own delivery strategy.

In fact, many smart ecommerce organizations send mass marketing emails from completely separate email sending domains than their transactional emails (by design) as part of their transactional email deliverability strategy. Transactional emails, by definintion, don't lend themselves well to the email deliverability rollercoaster mass marketing email sending domains typically endure where a/b testing, segmentation testing, and 'whateverthehell testing' (our word) is the norm. (for good reason)

>>How would you do this in terms of warm up and perhaps cool down? Would you need to warm up again if you haven't sent anything, or less than 300k, in say 2-3 weeks?

While general send volume numbers are ok, they can be grossly misleading. Case in point, we've seen portals sending tons of email to SOME segments of their list while allowing other segments to go completely cold. Then they send the same exact marketing email to the entire list and wonder why their deliverability drops off a cliff (from excessive bounces, abuse complaints, low opens, and poor CTR).


One important marketing email deliverability number we like to look in HubSpot is marketing email send frequency. Except, not the frequency you might think.

In addition to monitoring the traditional HubSpot email frequency CAP, we like to keep an eye on those contacts who may be falling behind on sends by using a BELOW SEND FREQUENCY THRESHOLD smartlist. We like to use 27-days as our threshold.

- see image


smart-list-BELOW-SEND-FREQUENCY-THRESHOLD-1-Per-Month-(should-be-empty).pngHubSpot Smart List: BELOW SEND FREQUENCY THRESHOLD - 1 Per Month (should be empty)

All that being said, marketing email sending domain/IP warm-up has more to do with email opens and clicks than send frequency. Establishing an email sending domain/IP as a non-threat -- the first step on the path to becoming a trusted sender -- is achieved by ramping up send volume while maintaining respectable open and click-through rates (CTR).

We like to use >30% opens and >10% CTR as our baseline minimum targets. But, we've seen email sending domains/IPs warm-up just fine while meeting baseline minimums as low as >20% opens and >3% CTR. Anything less borders on marketing email necromantic sorcery -- basically killing email contacts via email, then trying to convert those same dead contacts. haha Emoticono feliz

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Colaborador ocasional

Really great input Frank. Thank you so much!


Just a clarification from my side on why they are sending the same email to all of their contacts. By law, they are obliged to send information to their customers a few times per year with specific information related to their service. They could do this using the old postal service, but for various reasons they don't want to do this.


And in terms of Open Rate and CTR their average last year was OR 39% and CTR 21% for a total of 5.5 million emails sent.