Email Attachment Etiquette

Learn to use email attachments effectively, and ensure they're welcomed by the recipient


Email is a fantastic tool for sending all kinds of documents instantly all over the world. However, there are various potential problems you need to be aware of when sending attachments, especially if it's to somebody you don't already correspond with regularly.

People are generally more and more wary of opening attachments, especially from strangers, since they often conceal viruses, trojan horses, spyware and other "nasty" software. Even if the recipient is willing, your email may never get to them, as many corporate email systems will automatically filter emails with attachments as "spam", especially from sources outside of the company. There may also be limits to the size of email their email software can cope with, or on the file formats they're able to open.

The best way to send email with attachments

Follow these simple steps to maximise the chances of your email getting through, and getting noticed.

Remember that emails with attachments (especially large attachments) may take significantly longer to reach their intended recipients than smaller regular emails. Behind the scenes, emails are passed from server to server, gradually getting "closer" to their intended destination. This is called "store and forward" - each server in the chain takes a copy of the email and then works out the best place to send it next to move it closer to the final recipient, and then passes it on to that next server. Large emails take longer to send on each "hop" of the process.

How big an email attachment is too big?

Different email systems have different limits on the size of a single email. Emails above the limit may be silently rejected (i.e. you won't get any kind of warning, but they'll be discarded automatically before they ever get to the recipient) or may be "bounced" back to you with a warning such as "Message too large".

It's worth remembering that the sending process itself adds "overhead" to the size of the file, often as much as 30 to 40% of its original size. You'll never see that overhead, as it's concealed within the email system and the email transmission/receipt process, but it's there nevertheless. So for instance if the receiving email system is only able to cope with emails that are 10MB or less in size, then for practical purposes you should limit yourself to sending files that are no bigger than 6MB.

If your intended recipient is able to cope with ZIP files, that can be one way of cutting down on the size of attachments. Some file formats, such as PDF, text or Microsoft Word documents, will compress extremely well, and you're able to achieve substantial savings in file size. Other file formats, particularly for graphics and video, will hardly compress at all.

If you have any concerns about sending a large file, then why not upload it to an online file storage service instead? Then simply send the link to the file to your contact, rather than the file itself, and they can download it from the storage service at any time. Similarly, if you want to share photos, then why not upload them to an online photo album - many sites offer this type of service.

It's even more important to exercise restraint if your email is intended to go out to many people. For example, if you're emailing 100 people within the company, then by sending an attachment you're forcing the email system to cope with 100 very large emails at the same time, potentially putting a significant strain on resources. Sending 100 references to a file stored elsewhere (as long as this isn't against company policy) on the other hand takes practically no room at all.


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