What is the limit on the maximum size a single email may have?

The maximum size of an email sent from a ScalaHosting account is 50MB. This may seem like a restriction, but the limit exists for a few very good reasons. Let’s take a closer look at them.

Maintaining excellent performance

Email delivery continues to rely on SMTP – a communication protocol that can trace its roots back to the 1970s. Although we use email extensively in our everyday lives, the technology isn’t really suited to processing large volumes of data at once

By limiting the size of the messages servers need to handle, we’re ensuring reliable service and up-to-standards performance.

Setting up reliable anti-spam and security systems

In addition to working with a fairly old protocol, modern mail transfer agents also need to scan all passing emails for viruses and other threats. The larger the volume of information they need to go through, the slower the performance and the greater the chances of something malicious passing through the cracks.

Letting people communicate freely without worrying about storage space

Every email takes up space on a server. If users are allowed to make their messages as big as they want, it won’t be long before they exceed the storage quotas for their email accounts and hosting plans.

Improving uptime and security

Modern email communication makes use of a handful of networking ports. If they are asked to process a large volume of data at once, this could easily lead to deterioration in performance and, in extreme cases, bring the entire server down.

So far, we’ve talked about how the size of an email affects the service’s reliability, security, and performance. In addition to this, there are quite a few user experience considerations you need to keep in mind.

Larger emails tend to have higher spam scores

Because large emails can theoretically pose a threat to the entire server’s performance, they tend to be treated with more suspicion by spam filters. There are no set-in-concrete rules about when a filter might block an email, but, as a general rule, security systems tend to assign higher spam scores to big messages. 

Because of this, experts advise keeping the bodies of your emails below 100KB, especially if you run a newsletter with a significant number of subscribers.

The larger the email, the more time it needs to load

The more graphics, links, and multimedia content you put in your message, the longer it will need to be rendered correctly. Users with a slower internet connection might close the email before they’ve even seen it, defeating the purpose of sending it in the first place. 

Mobile devices are even less suitable for viewing heavy design components – something you need to bear in mind given that more than half of the internet traffic today passes through smartphones and tablets.

Email clients and service providers block large incoming messages

Just because you can send a message doesn’t necessarily mean the recipient will receive it. Both servers and clients have their own limitations that may block incoming messages from appearing in the recipient’s inbox. 

To avoid this, experts advise keeping attachments, images, and other heavy elements on an external server. Some code optimization should also help decrease the size of your emails.

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Working in the web hosting industry for over 13 years, Rado has inevitably got some insight into the industry. A digital marketer by education, Rado is always putting himself in the client's shoes, trying to see what's best for THEM first. A man of the fine detail, you can often find him spending 10+ minutes wondering over a missing comma or slightly skewed design.