Editing Microsoft Outlook (section)

== Internet standards compliance ==

=== HTML rendering ===
Outlook 2007 was the first Outlook to switch from [[Internet Explorer]] rendering engine to [[Microsoft Word 2007]]'s. This meant that [[HTML]] and [[Cascading Style Sheets]] (CSS) items not handled by Word were no longer supported. On the other hand, HTML messages composed in Word look as they appeared to the author.<ref>{{cite web |url=http://www.email-standards.org/clients/microsoft-outlook-2007/ |title=Microsoft Outlook 2007 Report &#124; Email Standards Project |work=email-standards.org |access-date=February 24, 2013 |archive-date=November 24, 2010 |archive-url=https://web.archive.org/web/20101124012315/http://www.email-standards.org/clients/microsoft-outlook-2007 |url-status=dead }}</ref> This affects publishing newsletters and reports, because they frequently use intricate HTML and CSS to form their layout. For example, forms can no longer be embedded in an Outlook email.

=== Support of CSS properties and HTML attributes ===
Outlook for Windows has very limited CSS support compared to various other e-mail clients. Neither [[Cascading Style Sheets#CSS 1|CSS1 (1996)]] nor [[Cascading Style Sheets#CSS 2|CSS2 (1998)]] specifications are fully implemented and many CSS properties can only to be used with certain HTML elements for the desired effect.<ref name="campaignmonitor">{{cite web|url=http://www.campaignmonitor.com/css/|title=CSS Support Guide for Email Clients – Campaign Monitor|access-date=September 6, 2012|archive-date=January 15, 2021|archive-url=https://web.archive.org/web/20210115055555/https://www.campaignmonitor.com/css/|url-status=live}}</ref> Some HTML attributes help achieve proper rendering of e-mails in Outlook, but most of these attributes are already deprecated in the [[HTML#HTML version timeline|HTML 4.0 specifications (1997)]].<ref>{{cite web|url=http://www.w3.org/TR/1998/REC-html40-19980424/|title=HTML 4.0 Specification|access-date=September 6, 2012|archive-date=July 27, 2008|archive-url=https://web.archive.org/web/20080727143129/http://www.w3.org/TR/1998/REC-html40-19980424/|url-status=live}}</ref> In order to achieve the best compatibility with Outlook, most HTML e-mails are created using multiple boxed tables, as the table element and its sub-elements support the width and height property in Outlook. No improvements have been made towards a more standards-compliant email client since the release of Outlook 2007.<ref>{{cite web |url=https://www.campaignmonitor.com/blog/post/3769/a-designers-guide-to-outlook-2013|title=A designer's guide to Outlook 2013 and Office 365 |access-date=July 22, 2014|url-status=dead|archive-date=November 28, 2014|archive-url=https://web.archive.org/web/20141128231246/https://www.campaignmonitor.com/blog/post/3769/a-designers-guide-to-outlook-2013}}</ref>

=== Transport Neutral Encapsulation Format ===
{{Main|Transport Neutral Encapsulation Format}}
Outlook and Exchange Server internally handle messages, appointments, and items as objects in a data model which is derived from the old proprietary [[Microsoft Mail]] system, the [[Rich Text Format]] from [[Microsoft Word]] and the complex [[Object linking and embedding|OLE]] general data model.<ref>Outlook Data Model Reference (page on the MailItem object class members), MSDN development documentation, [http://msdn.microsoft.com/en-us/library/ff861252.aspx] {{Webarchive|url=https://web.archive.org/web/20111123213722/http://msdn.microsoft.com/en-us/library/ff861252.aspx|date=November 23, 2011}}, retrieved May 2011</ref> When these programs interface with other protocols such as the various Internet and [[X.400]] protocols, they try to map this internal model onto those protocols in a way that can be reversed if the ultimate recipient is also running Outlook or Exchange.<ref name="tnefphilosophy">[http://msdn.microsoft.com/en-us/library/cc815562%28v=office.14%29.aspx Transport-Neutral Encapsulation Format (TNEF) | Outlook 2010] {{Webarchive|url=https://web.archive.org/web/20170520012521/https://msdn.microsoft.com/en-us/library/cc815562(v=office.14).aspx |date=May 20, 2017 }}. ''Microsoft''. July 28, 2014. Retrieved May 29, 2020.</ref>

This focus on the possibility that emails and other items will ultimately be converted back to Microsoft Mail format is so extreme that if Outlook/Exchange cannot figure out a way to encode the complete data in the standard format, it simply encodes the entire message/item in a proprietary binary format called [[Transport Neutral Encapsulation Format]] (TNEF) and sends this as an attached file (usually named "winmail.dat") to an otherwise incomplete rendering of the mail/item. If the recipient is Outlook/Exchange it can simply discard the incomplete outer message and use the encapsulated data directly, but if the recipient is any other program, the message received will be incomplete because the data in the TNEF attachment will be of little use without the Microsoft software for which it was created.<ref name="tnefphilosophy" /> As a workaround, numerous tools for partially decoding TNEF files exist.

=== Calendar compatibility ===
Outlook does not fully support data and syncing specifications for calendaring and contacts, such as [[iCalendar]], [[CalDAV]], [[SyncML]], and [[vCard]] 3.0. Outlook 2007 claims to be fully iCalendar compliant; however, it does not support all core objects, such as VTODO or VJOURNAL.<ref>{{cite web|url=https://www.microsoft.com/office/editions/prodinfo/compare.mspx#EBAA|title=Microsoft Office 2003 editions comparison|publisher=Microsoft|access-date=October 3, 2008|archive-date=January 7, 2021|archive-url=https://web.archive.org/web/20210107173129/http://www.microsoft.com/office/editions/prodinfo/compare.mspx#EBAA|url-status=live}}</ref> Also, Outlook supports vCard 2.1 and does not support multiple contacts in the vCard format as a single file. Outlook has also been criticized for having proprietary "Outlook extensions" to these Internet standards.

=== .msg format ===

Outlook (both the web version and recent non-web versions) promotes the usage of a proprietary <code>.msg</code> format<ref name=msgspec>{{cite web|url=https://docs.microsoft.com/en-us/openspecs/exchange_server_protocols/ms-oxmsg/b046868c-9fbf-41ae-9ffb-8de2bd4eec82|title=[MS-OXMSG]: Outlook Item (.msg) File Format|date=February 15, 2022 }}</ref> to save individual emails, instead of the standard [[.eml]] format. Messages use {{Mono|.msg}} by default when saved to disk or forwarded as attachments. Compatibility with past or future Outlook versions is not documented nor guaranteed;<ref>{{cite web|url=https://answers.microsoft.com/en-us/outlook_com/forum/oemail-osend/archiving-emails-in-msg-format/974b19f1-dc45-4866-aeb4-ac36e46e4636|author=Dane (MS)|title=Archiving emails in msg format|access-date=May 20, 2021|archive-date=May 20, 2021|archive-url=https://web.archive.org/web/20210520065856/https://answers.microsoft.com/en-us/outlook_com/forum/oemail-osend/archiving-emails-in-msg-format/974b19f1-dc45-4866-aeb4-ac36e46e4636|url-status=live}}</ref> the format saw over 10 versions released since version 1 in 2008.<ref name=msgspec/>

The standard {{Mono|.eml}} format replicates the format of emails as used for transmission and is therefore compatible with any email client which uses the normal protocols. Standard-compliant email clients, like [[Mozilla Thunderbird]], use additional headers to store software-specific information related e.g. to the local storage of the email, while keeping the file plain-text, so that it can be read in any [[text editor]] and searched or indexed like any document by any other software.