Which File format is Supported by SMTP?

Are you still using basic email services like Microsoft Outlook for all your emailing needs? Then, you might be aware that there is this protocol called SMTP which sends emails between servers. Now, while this protocol is brilliant for sending text messages between servers, it can also be used to send file attachments that are available on your PC. So, want to know which file format is supported by SMTP?

Well then, just follow this article till the end.

Which file format is supported by SMTP?

Sending and receiving emails is one of the basic tasks that we perform in our day-to-day life. And with people using the SMTP protocol instead of the new HTTPS-based protocols, it becomes necessary to get a clear insight into which file format is supported by SMTP.

So, to help you with the same, we have listed down some of the file formats that are supported by SMTP.

Now, these are some of the file formats that SMTP can easily support as attachments that can be further sent to the recipient.

Although, getting to know each file format can help you utilize them to their 100% potential. So, below is a short introduction to each of them.

What are PDF, DOC, XLS, JPG, PNG, MP3, and MP4 file formats?


Portable Document Format popularly known as PDF is a file format that is widely used by users to preserve their important documents in a digital format. Now, this format is especially known for its no formatting policy, meaning the layout, fonts, style etc, will be preserved as it is, which again makes it one of the best file formats to be attached to emails. 

However, it should be noted that most of the email clients have a file limit for the attachments. So, we advise you to only attach files that are decent in size.


Doc file is a well-known Microsoft Word document file format that is supported by almost every word processor on the planet.

This file is basically used for writing purposes, but still, a user can easily drop in some other elements like; images, videos, tables and charts. Also not to mention, this file format also includes formatting information such as font, size, and color.

Though, like PDF, you should always consider checking the file size of the attached DOC file, because SMTP may not support big file sizes. Also, do check that the recipient has dedicated software to open the DOC file.


XLS is a file format specially designed for creating and editing spreadsheets. It is a well-known file format for the Microsoft Office software “Excel.”

Now, this file format when opened up using supported software can show you data inside cells, along with different elements like formulas, charts and images. You can also notice information such as font, size and color, which can be easily used to control the appearance of the data inside a spreadsheet.

However, like PDF and DOC, it should only be attached to an email with a decent file size. Plus, the receiver should have an app installed on his/her device that supports XLS.


Joint Photographic Experts Group shortly known as JPG is a raster-based image file format which is preferred by most photographers and bloggers. 

The main USP of this file format is that it uses lossy compression but still can handle a wide range of color and tones, which makes it a perfect choice for photographs and other images that consists wide range of colors.

However, like PDF, DOC and XLS, a JPG file should also be customized with the appropriate file size.


Portable Network Graphics (PNG) is a raster-based lossless file format that was created as an improved version of GIF.

This file format is known for its versatility as it supports grayscale images, palette-based images, and full-color non-palette-based RGB and RGBA images. 

PNG also supports transparency which allows an image to have a semi-transparent or transparent area. Not to mention, it is also supported by most web browsers, image editors, and other applications.

Like the above-mentioned formats, a user should take care of the file size limit and compress it before sending it to the other party.


MP3 is one of the most known audio file formats that is supported by every media device on the planet, which makes it a perfect fit for all audio-sharing needs. 

Due to its compressed form, it becomes really easy for end users to share or download files from the internet. 

However, due to its lossy compression feature, there is a minute loss in audio quality. But it is fairly acceptable and can only be known to experts. 


MPEG-4 commonly known as MP4 is a video file format that is widely used by many users as it is supported by most media devices. 

It is a great option if you are looking to share videos in a compressed form because most of the media-sharing utilities have file size limits. 

Plus, if your MP4 file is big then you should consider compressing it before sharing.


SMTP as an email protocol can prove to be a boon, only if you are using the correct file formats that are supported by the protocol.

And after this discussion, we are sure that you must have gained a good amount of knowledge on the file formats you should use while using the SMTP protocol.

Frequently Asked Questions:

What is the main purpose of SMTP?

The SMTP protocol is used to send and receive emails.

Does SMTP require a server?

Yes, without a dedicated SMTP server, you cannot send emails to their destination.

What are the two primary components of SMTP?

The two primary components of SMTP are; User Agent (UA) and Mail Transfer Agent (MTA).

What is the best SMTP port?

Port 587 is the best SMTP port.


  • Ashish Simon

    Hello folks! I am Ashish Pawar – A graduate from the field of Arts but an avid admirer of all things tech; therefore, made a leap into writing technical articles for ‘how-to’ guides and ‘informational content’ with the aim to make tech understandable for the masses. I have been in this field for more than a year now. My ideology is that even a layman should be able to understand tech easily. As a creative individual I am also passionately engaged in activities like photography, music, and dance.