What Is A Suggested Maximum Size Of A Rule Base?

Every email sending provider has its own maximum email size limit. However, in that location is no unique standard – limits are dictated mostly by performance and security reasons. At that place are many things you should go along in mind when preparing your e-mail notifications or newsletters: from the maximum size of file attachments and HTML part to the e-mail client your recipients will virtually likely use. Likewise, there are some not then obvious factors, which impact the actual electronic mail size and deliverability. In this article, we take gathered replies to the virtually common related questions:

What is the recommended size for the email body and attachments?
What are the limits of different electronic mail clients and sending providers?
How do the embedded images affect electronic mail size, spam score, and deliverability?
What are the common issues and errors related to electronic mail size and how to handle them?

As well, nosotros have implemented an e-mail size limit for Mailtrap: let'southward review how information technology works and how it can assistance you with testing your e-mail deliverability.

Types of email size limits

E-mail size limits are used for iii main reasons:

Functioning. Email systems are not designed to transfer large volumes of information. They deal with SMTP, which is a quite outdated protocol. Most of the systems are not able to process multiple data sources at once. In addition, mail transfer agents often browse incoming information for viruses and other potential risks, which also takes resources and affects organization performance.
Database/storage size. Electronic mail data should be stored on a server (either cloud or local). This is why non but the message itself but as well the inbox equally a whole has its own limits.
Security. Points one and ii on our listing also pb to potential security vulnerabilities. Email systems usually use a limited number of ports to think data. This makes them candidates for DoS (deprival of service) attacks: a huge amount of big messages tin can take the whole system downwardly. This is besides known as an email flop.

When preparing either transactional or marketing emails, you should consider 2 limits:

limit to transport a bulletin (your email system)
limit to retrieve a message (your recipients' mail arrangement).

For example, if your email service is able to send messages upwards to fifteen MB but the email recipient tin recollect messages merely up to 10 MB, information technology's obvious that your email should not exceed 10MB. Otherwise, the email will be rejected. It is useful to know the assart for your recipient's incoming messages.

If you piece of work with a large database of e-mail addresses to transport transactional or marketing emails and don't have such details most your recipients, you should follow a general rule: ship messages that don't exceed 10 MB.

Limits for popular email sending providers and clients like Gmail, Outlook, Sendgrid, etc.

Email client	Sending and inbound size limits
AOL	25 MB
Apple Mail (iCloud)	20 MB
Gmail	25 MB
GMX	50 MB
Outlook/Role 365	twenty MB (10 MB for Exchange accounts), with up to 150 MB in Role 365
ProtonMail	25 MB
Thunderbird	no
Yahoo	25 MB
Zoho Mail	20 MB

Email clients size limits

E-mail sending provider	Sending size limit	Special notes
AWS SES	ten MB
Mailgun	25 MB
Mandrill	25 MB
Postmark	ten MB	TextBody and HtmlBody tin each be up to 5 MB each
Sendgrid	30 MB

ESPs size limits

You tin can run into that most e-mail clients are capable of retrieving 20 – 25 MB of email information. Information technology's a pretty rare situation when y'all demand to send a mass electronic mail with large attachments. Just it is still possible when you lot send numerous booking or order confirmations, for example. However, as well general deliverability, in that location are few more than concerns related to sending big messages. Spam score and rendering issues are the most important. Moreover, some ESPs like Postmark have boosted limits for the electronic mail body size.

What else should y'all consider about the size of your e-mail?

Taking care to create a bulletin that volition be successfully delivered to your recipients, you should also think of which folder it will go to, how quickly it will be delivered, and how happy your recipients will be.

Inspect Your Emails

Spam score

Avoiding spam filters and targeting the primary folder of your recipient'due south inbox is one of the trickiest things in email handling. You won't find strict and ubiquitous criteria for spam detection. However, in that location is a list of common "anti-spam" rules, and the size-related points are at the meridian of it.

Technically, there is no bulletin body limit in the SMTP protocol. Still, some providers have their own limits. For example, Postmark allows the HTML and text parts each to be 5 MB, while Gmail clips the trunk of messages over 102 KB.

Many tests by various providers prove the correlation between electronic mail size and deliverability. In about cases, messages with a torso over 100 – 150 KB trigger spam filters. So, the mutual recommendation is to go on email body size between 15 KB and 100 KB.

Rendering problems

Another aspect of large emails is their loading and/or rendering speed. Your recipients do not always have access to a high-speed connection, and a long-lasting message loading process might cause irritation. In improver, in many email clients, a large email body might be rendered but partially, and your recipient will see but parts of images or clipped content. This might strongly harm your customer digital experience and leave a bad general impression.

Notwithstanding the numerous limitations and hidden constraints, there are common rules on building well-performing emails. The first of these is to decrease and optimize email body size.

What does affect the email size and how can you optimize it?

Each chemical element of the message and the way it'south implemented impacts e-mail size.

Attachments. With attachments everything is straightforward. These are enclosed files and don't affect the electronic mail body size. The total email limit usually includes all of the attachments. The best option is to upload files y'all demand to transfer to the cloud and put a link into your message. Due to security issues, many file types are blocked or are considered dangerous (including .doc, .xls, and .pdf).
Images and other embedded elements. Even simple notifications usually comprise images, at to the lowest degree your company logo. Their size depends on the image format and the way the image is embedded into the message. We had a closer wait at this topic in this article. In short, wherever possible, link to an image hosted on an external server (in the HTML, so it volition exist displayed every bit role of the message).
Encoding. MIME-encoded (base64) messages add together 33% to your email size. Keep this in mind when coding a multipart bulletin.
Other. Every single message chemical element affects its general size. Message headers, signatures, formatting – all of these add extra kilobytes.

Rules of a perfect email

Considering the in a higher place mentioned limits and dependencies, nosotros have created a short email size optimization checklist. Here are the best practices for building a well-performing e-mail in terms of size:

Continue the email body from 15 KB to 100 KB.
Don't add together attachments over 10 MB. If possible – upload your files to the external server and make them available online/ for download using a link.
Don't overuse images, GIFs, and other multimedia content.
Remember that well-nigh 42% of emails are opened on mobile devices. Keep this in mind when creating e-mail templates. They should exist responsive. Using a responsive email framework or an email builder can save you nerves and kilobytes.

Check email size in Mailtrap before sending

Fifty-fifty if you followed all recommendations and have crafted the perfect message, checking its size is not an easy task. Whether you are coding a message in your app or preparing a template to send via Gmail, you need to use a third-political party tool, actually send your message, or download it so to explore its size.

If you apply Mailtrap for testing your emails before sending them to your real recipients, yous tin easily check both the e-mail body and attachment size.

check email body and attachment size in Mailtrap

As soon as your examination bulletin is trapped in your virtual inbox, the total e-mail size is displayed along with the message headers. If your message has attachments, you will see a list of them with file names and sizes.

Also, Mailtrap has email size limits, which depend on your billing plan. Y'all tin test messages upwardly to 5 MB (total email size with attachments) for free. The maximum possible email size to test is express to 25 MB.

Instead of offering a conclusion, let'due south review the most common SMTP errors related to the mail size. There are two of them:

Error lawmaking	Clarification	Reason and how to solve
Error 523	The Recipient's mailbox cannot receive messages this big.	Your message exceeds the size limit of your recipient's server. Bank check the size of the email body and attachments. Utilise the recommendations above to optimize it.
Error 552	Requested mail action aborted: exceeded storage allotment or size of the incoming message exceeds the incoming size limit.	The email box of your recipient is full. In this case you lot have nothing to do: your recipient should make clean up his or her inbox.Or your message exceeds the limit set up by the administrator. Check the size of your message and optimize information technology.

SMTP codes volition be completed with boosted numbers and messages so you will be able to sympathize the exact reason. The general rule is to keep your email size as compact every bit possible, check, and test it before sending to real recipients.