<base>
Specifies the base URL to use for all relative URLs in a document.
Outlook
Windows
2003
2007
2010
2013
2016
2019
Windows Mail
2021-12
macOS
16.56
Outlook.com
2021-12
Android
2021-12
Samsung Email
Android
6.0
Mozilla Thunderbird
macOS
91.2
HEY
Desktop Webmail
2021-12
LaPoste.net
Desktop Webmail
2021-12
1&1
Desktop Webmail
2022-11
Android
2022-11
Mail.ru
Desktop Webmail
2021-12