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How Does Email Size Affect Deliverability?

Email size and deliverability

What could be more important for an email marketer than knowing his or her carefully planned email campaign is being successfully delivered and receiving customer attention? Spam filters can make emailing difficult by requiring that special rules are followed before sending out an email campaign. The question, “How do I make my emails spam-filter friendly?” is quite common among email marketers.

Mailigen email deliverability team knows there are many criteria to follow in order to avoid spam filters and get your email campaigns delivered. Is email size one of them?

At what point does email file size cause deliverability issues?

Yes, email size plays a considerable role in email deliverability. Spam filters take email size as one of the criteria for marking emails as spam.

To put it more plainly, how many Kb can you send in an email, to avoid it ending up in the spam folder?

The Acid email team accepted the challenge of clarifying the perfect email size. After several tests, they found out that the perfect sized email ranges from 15 KB to 100 KB. So, if you are wondering how many KB you can send in an email, keeping it under 100 KB increases the probability that will keep you out of the spam box. However, exceeding the email size limit by even a few bytes will make a difference. The study shows that whether an email is 600 KB or 110 KB, it will still get caught in the same (seven) spam filters, just because it is over 100 KB.

Take this into account if sending emails to:

  • Apple Mail (5, 6, 7)
  • Outlook (2007, 2010)
  • Google Apps
  • Yahoo

A study carried out by CheetahMail found identical results. If you are sending email campaigns to webmail providers like Gmail, Yahoo!, AOL and Outlook, it is important to keep email message size below 100 KB. One byte more will probably cost you a trip to the spam folder.

How can I avoid email deliverability issues before they happen?

In order to ensure that your emails get delivered in your subscribers’ inbox and not drained in spam filters, keep your emails short, clear and to the point. Removing all unnecessary photos, attachments and other components that may slow down the loading time and increase the size.

Keeping the email size under 100 KB is not just baseless rule. There are other advantages to making your email light, for example, shorter loading time. If the email consists of large and heavy images, the loading time will increase. Emails opened on mobiles and tablets increase by the minute, and the loading speed of your email campaign on those gadgets will be slower than on a desktop. Take that into account before testing your subscribers’ patience!

Keep your email size in check at Mailigen

At this point, marketers may ask, “How do I know the size of my email?”

Email size is made of all its components, including the basic email template and all necessary text, images, links and attachments. Marketers designing their campaigns are well aware of the size of images and attachments, because often they are in charge of making or adding them. It is more difficult dealing with text and links. The size of text varies not only according to the length but also the size of the characters, their color and other formatting options, and it was not possible to see the exact size of an email template when working with these components. Until now!

The Mailigen team has released a tiny new feature. In the fifth step of campaign planning wizard, you will be able to see the approximate size of your email campaign. To avoid deliverability issues, marketers will be able to see how large their email template, HTML code and embedded images, actually is. This new feature will allow you to make sure you keep bellow 100KB and therefore reach more of your subscribers.

Email size and deliverability

Choose the right image sizes

Now that you know how many KB you can send in an email, here are a few simple rules you should follow when working with different email components. Images, for example!

There are three golden rules for using an image in an email:

1. Keep in mind that the safest email size limit (images included!) is less than 100 KB

This is like solving a simple math equation. No matter how large or how many images, as long as the whole email message size is less than 100 KB, you are safe. To help follow these principles, emails sent using Mailigen don’t actually include images, but they are loaded from our server on individual recipients computer when an email is opened. But in case you are using inline image feature, then images are hard-coded inside the HTML code and email will actually be heavier.

2. Use .png format instead of .jpg for your images

The .png format allows you to optimize images by making them lighter without a change in quality.

3. Never put a single image in your email without any text

Spammers usually use large images as a text container, because bots and programs that check content cannot read images. If your email contains only images without any text, your campaign will most likely land in the spam folder. We suggest you use proportions of 50/50 or 60/40 text to image.

What about attachments?

Large attachments will be recognized as potentially harmful by many email providers like Gmail, and therefore could land a message in the spam folder. If you decide to use attachments in your email, make sure the size of each attachment is not larger than 2 MB, and the total size of attachments is no more than 10 MB.

We suggest avoiding attachments altogether, using links to stored files or special landing pages. Motivate your subscribers to click in order to increase your CTR (click-through rate), website visits and brand awareness.

Conclusions for great deliverability

Spam filters are often misunderstood as an aggravating obstacle for reaching a customer, yet their only aim is to improve email quality all over the world. Make your emails clear, straightforward messages, removing unnecessary spacing, attachments, and other components.

Enjoy our new email size preview feature while boosting your email deliverability! Include necessary information and eye-catching pictures while keeping your email size in check to make your contribution to email quality and reach your customers effortlessly.

We want to remind you that email size has an impact on email deliverability, but we don’t want to stress you out by trying to squeeze your creative email campaign into 100 KB just out of fear of spam filters. Keep your subject line, email content and links clear, avoiding spam words, sending only permission-based emails and following other rules mentioned in our anti-spam policy.

For more information about spam and email delivery, or if you have other questions, contact our Mailigen support team.

How Does Email Size Affect Deliverability?
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    April 27, 2015 at 9:51 am

    Very Helpfully blog for Email Size Affect Deliverability!!! Thanks to sharing a good blog.

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