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Allowed attachment types for sending email in Azure Communication Services

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The SendMail operation allows the option for the sender to add attachments to an outgoing email. Along with the content itself, the sender must include the file attachment type by using the Multipurpose Internet Mail Extensions (MIME) standard when making a request with an attachment. Many common file types are accepted, such as Word documents, Excel spreadsheets, image and video formats, contacts, and calendar invites.

What is a MIME type?

MIME types are a way to identify the type of data that's being sent over the internet. When users send email requests by using Azure Communication Services, they can specify the MIME type of the email content so that the recipient's email client can properly display and interpret the message. If an email message includes an attachment, the MIME type is set to the appropriate file type (for example, application/pdf for a PDF document).

Developers can ensure that the recipient's email client properly formats and interprets the email message by using MIME types, irrespective of the software or platform that the system is using. This information helps ensure that the email message is delivered correctly and that the recipient can access the content as intended. Using MIME types can also help to improve the security of email communications, because they can indicate whether an email message includes executable content or other potentially harmful elements.

MIME types are a critical component of email communication. By using MIME types with Azure Communication Services, developers can help ensure that their email messages are delivered correctly and securely.

Allowed attachment types

This table lists common supported file extensions and their corresponding MIME types for email attachments in Azure Communication Services:

File extension Description MIME type
.3gp 3GPP multimedia file video/3gpp
.3g2 3GPP2 multimedia file video/3gpp2
.7z 7-Zip compressed file application/x-7z-compressed
.aac AAC audio audio/aac
.avi AVI video file video/x-msvideo
.bmp BMP image image/bmp
.csv Comma-separated values text/csv
.doc Microsoft Word document (97-2003) application/msword
.docm Microsoft Word macro-enabled document application/vnd.ms-word.document.macroEnabled.12
.docx Microsoft Word document (2007 or later) application/vnd.openxmlformats-officedocument.wordprocessingml.document
.eot Embedded OpenType font application/vnd.ms-fontobject
.epub EPUB e-book file application/epub+zip
.gif GIF image image/gif
.gz GZIP compressed file application/gzip
.ico Icon file image/vnd.microsoft.icon
.ics iCalendar file text/calendar
.jpg, .jpeg JPEG image image/jpeg
.json JSON data application/json
.mid, .midi MIDI audio file audio/midi
.mp3 MP3 audio file audio/mpeg
.mp4 MP4 video file video/mp4
.mpeg MPEG video file video/mpeg
.oga Ogg audio file audio/ogg
.ogv Ogg video file video/ogg
.ogx Ogg file application/ogg
.one Microsoft OneNote file application/onenote
.opus Opus audio file audio/opus
.otf OpenType font font/otf
.pdf PDF document application/pdf
.png PNG image image/png
.ppsm PowerPoint macro-enabled slideshow application/vnd.ms-powerpoint.slideshow.macroEnabled.12
.ppsx PowerPoint slideshow application/vnd.openxmlformats-officedocument.presentationml.slideshow
.ppt PowerPoint presentation (97-2003) application/vnd.ms-powerpoint
.pptm PowerPoint macro-enabled presentation application/vnd.ms-powerpoint.presentation.macroEnabled.12
.pptx PowerPoint presentation (2007 or later) application/vnd.openxmlformats-officedocument.presentationml.presentation
.pub Microsoft Publisher document application/vnd.ms-publisher
.rar RAR compressed file application/x-rar-compressed
.rpmsg Outlook email message application/vnd.ms-outlook
.rtf Rich Text Format document application/rtf
.svg Scalable Vector Graphics image image/svg+xml
.tar Tar archive file application/x-tar
.tif, .tiff Tagged Image File Format image/tiff
.ttf TrueType font font/ttf
.txt Text document text/plain
.vsd Microsoft Visio drawing application/vnd.visio
.wav Waveform Audio File Format audio/wav
.weba WebM audio file audio/webm
.webm WebM video file video/webm
.webp WebP image file image/webp
.wma Windows Media Audio file audio/x-ms-wma
.wmv Windows Media Video file video/x-ms-wmv
.woff Web Open Font Format font/woff
.woff2 Web Open Font Format 2.0 font/woff2
.xls Microsoft Excel spreadsheet (97-2003) application/vnd.ms-excel
.xlsb Microsoft Excel binary spreadsheet application/vnd.ms-excel.sheet.binary.macroEnabled.12
.xlsm Microsoft Excel macro-enabled spreadsheet application/vnd.ms-excel.sheet.macroEnabled.12
.xlsx Microsoft Excel spreadsheet (Open XML) application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
.xml Extensible Markup Language file application/xml, text/xml
.zip ZIP archive application/zip

There are many other file extensions and MIME types that you can use for email attachments. However, this list includes accepted types for sending attachments in the SendMail operation.

Some email clients and servers might have limitations or restrictions on file size and types that could result in the failure of email delivery. Ensure that the recipient can accept the email attachment, or refer to the documentation for the recipient's email provider.

Additional information

The Internet Assigned Numbers Authority (IANA) is a department of the Internet Corporation for Assigned Names and Numbers (ICANN). IANA is responsible for the global coordination of various internet protocols and resources, including the management and registration of MIME types.

IANA maintains a registry of standardized MIME types. The registry includes a unique identifier for each MIME type, a short description of its purpose, and the associated file extensions. For the most up-to-date information about MIME types, including the definitive list of media types, go to the IANA website.

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