How to Email Large Files Securely

By Hiren Mehta
— Last Updated: 2020-06-10T08:20:39+00:00

It is very frustrating when you need to transfer a large file immediately and using a thumb drive is not an option. Most common email providers don’t let you send large files as an attachment, so you’ll probably have to hunt around to find a file-sharing service.

Even if you find one, though, you may find that security is a problem: not all these services, especially the free ones, will have the encryption you need to make sure no third parties can access your document or picture.

In this guide, we show you how to email large files securely. Note that by “large,” we mean files that exceed 250MB, which is several times over the limits imposed by many popular email providers. With the help of this guide, you will be able to send entire disk images without actually sending the disk itself.

The best part is that in case of each of the providers that we are going to talk about, the recipients don’t need to register for an account. They will still be able to get your file without signing up.

Security Aspects to Consider

Since we are not using the mailbox space to store the large files themselves, there is the question of how secure the servers of cloud storage websites themselves are. Some providers are notorious for giving little care to security. Not just your login credentials but also the actual data that you store can get stolen.

In case of email, phishing scams as well other forms of skulduggery are common. Depending on how tech-savvy your receiver is, he may not be able to tell apart the difference and this can lead to a lot of problems when they open an email they thought was from you.

To make sure everyone stays safe, it pays to keep the following in mind:

  • Whether sent emails can be easily identified as authentic
  • If there are mechanisms in place that restrict access to only the addressee
  • Any systems in place to guarantee file integrity
  • If the system keeps a log so you can check for any unauthorized snooping

That said, let’s go through a few providers that allow you to email large files securely.


DropSend is an entirely browser-based app that requires no downloads. It’s very user-friendly and fast, plus it also has mobile apps for Android and iOS. If you do prefer to work from your desktop, DropSend offers clients for the Mac and PC as well as a plug-in for Microsoft Outlook.

DropSend uses 256-bit AES encryption and supports files that are up to 4GB with the free personal plan (8GB for paying customers), making it less useful when you want to send across something equivalent to a Blu-ray DVD or even a dual-layer DVD in one file. A free trial is available.


FileMail works in a similar way as DropSend except that it allows for even larger files. However, its paid plans are more expensive than those of DropSend. You can even use it on your own website, allowing visitors to send you large files by filling out a customizable form. There is also an API available for developers.

FileMail uses 128-bit at-rest encryption, however, the document that states this hasn’t been updated since 2013. Free plans cap the maximum file size at 30GB whereas paid plans claim to support an “unlimited” file size.


OneDrive is more popular as an online storage medium than specifically sending files via e-mail. With OneDrive, the maximum file size allowed depends on the tool that you are using, such as, Windows’ own file explorer, desktop app, mobile app, etc. In most cases, the upper limit on a single file is set at 10GB (see our OneDrive file size limit guide).

OneDrive offers many access control features for sharing files. Microsoft also claims that they save copies of each file on different drives and servers. This allows you to access them even in case of a hardware failure.


SendThisFile places limits on the amount of transfers that you do rather than on the individual file size itself. It does use AES-256 encryption at rest and 128-bit TLS encryption for end-to-end transmission. However, even the top-end enterprise plan (which costs $99.95 per month) will allow you to transfer only about 500GB of data.

A free trial is available which allows you to transfer 50GB of data. You can even sign up using your Facebook, LinkedIn or Google+ account.


Like OneDrive, Dropbox too is considered to be more of an online storage medium suited for all types (and sizes) of files. When you sign up for a Dropbox account, you get a certain amount of storage space allocated to you. This limit can be a something of a bottleneck compared to the size of the file that you want to upload.

Files that you upload using the desktop app or mobile app have no set limits on their size. Those that are uploaded using the browser need to be 20GB or smaller (read our Dropbox file size limit guide).

A lot has been said about Dropbox’s security practices and problems. User credentials have been stolen in the past and even routine maintenance has often resulted in a lot of frustration. In terms of encryption it is similar to SendThisFile.

Creating a Shared Folder in Dropbox

For example, one such poorly implemented measure is that only the contents of the files are encrypted, not their metadata. So if someone has access to Dropbox’s storage media, it may not be possible to directly examine the contents of your files but educated guesses can certainly be made based on the filename, the size, the upload date, etc.

Dropbox claims that their storage servers are located in data centers across the United States. It complies with the EU-U.S. privacy shield program and the U.S.-Swiss safe harbor framework as well.

If you are using a Mac, you will need to allow Dropbox to have access to your keychain. Without this access, it will not start. The service claims that the access is needed to verify your account and to further secure the Dropbox application settings.


The home page of MEGA is a tad heavy to load. However, you can immediately get started uploading files by dragging and dropping them right onto the homepage itself. You can of course choose to use the file uploader too if you want. Like Dropbox, MEGA too does not claim to place any individual limit on the file size (read our Dropbox vs MEGA comparison).

MEGA relies heavily on end-to-end encryption, even if you are uploading files using the browser or a mobile device. The private keys used for the encryption and decryption process never leave the user’s device, MEGA claims it does not hold them on its servers.

It even encourages users to adopt their own backup practices and not solely rely on them. In their support pages, they have given a list of possible risks and attacks so that you as a user are aware of what can likely happen in the worst possible case.


When looking purely from a security perspective, MEGA seems to be a very good tried-and-tested option. However, it does not offer as many third-party integrations as Dropbox does. The business plans OneDrive offers, especially when combined with Office 365, give you a variety of applications but this may be overkill for some.

In case of the lesser known options, like DropSend, FileMail and SendThisFile, you may feel more secure not having come across any news about them suffering from cyberattacks. However, sooner or later they will eventually suffer such an attack and only then will you know whether their defenses are up to the task.

So the choice begins with a single question: do you feel safer in going for a relatively unknown provider whose security may not have been tested yet or in going for an already popular provider who might have been targeted by hackers at least once so far?

Once that is clear, you next need to take into account the features, pricing and file size limitations of the respective provider. That will help you zero in on one of the six providers we have mentioned here.

We hope you enjoyed reading the guide. Let us know what your thoughts are about using these services in the comments below.