Exchange 2016: How to force it use UTF-8 encoding

In order to minimize the number of possible problems with message encode (e.g. "?" instead of Cyrillic symbols), I recommend to set up an unified universal encoding in the Exchange - UTF-8.

Quotation from the TechNet article regarding choosing encoding for outgoing emails:

"Exchange uses the order of precedence as described in the following list to determine the message encoding options for outgoing messages sent to recipients outside the Exchange organization"

1. Mail user or mail contact settings

There are no specific attributes to determine encoding for MailContact and MailUser.

2. Outlook or Outlook Web App settings

The most convenient way to configure user's Outlook is using GPO. There are two options: Administrative Templates and registry.

Administrative Template:

User Configuration/Policies/Administrative Templates/Microsoft Outlook 201*/Outlook Options/Mail Format/International Options | Auto-select encoding for outgoing messages -> Enabled
User Configuration/Policies/Administrative Templates/Microsoft Outlook 201*/Outlook Options/Mail Format/International Options | Encoding for outgoing messages -> Enabled + "Unicode (UTF-8)"
User Configuration/Policies/Administrative Templates/Microsoft Outlook 201*/Outlook Options/Mail Format/International Options | Euro encoding for outgoing messages -> Enabled + "Send messages as UTF 8"

BUT in my case Administrative Template (for 2013 and 2016 versions) works unexpectedly (tested in three environments) and the "Auto-select encoding for outgoing messages" is always Disabled.

Registry

So, I decide to do it by registry:

"User Configuration\Preferences\Windows Settings\Registry\Software\Microsoft\Office\1*.0\Outlook\Options\MSHTML\International\", "autodetect_codepageout" = 1 (REG_DWORD)

"User Configuration\Preferences\Windows Settings\Registry\Software\Microsoft\Office\1*.0\Outlook\Options\MSHTML\International\", "autodetect_ignoreeuro" = 0 (REG_DWORD)

"User Configuration\Preferences\Windows Settings\Registry\Software\Microsoft\Office\1*.0\Outlook\Options\MSHTML\International\", "default_codepageout" = 65001 (REG_DWORD)

And now Outlook looks good, as I expected.

Configure OWA (Outlook on the Web):

Get-OwaVirtualDirectory | Set-OwaVirtualDirectory -OutboundCharset AlwaysUTF8
iisreset /noforce

3. Remote domain settings

Get-RemoteDomain | Set-RemoteDomain -CharacterSet utf-8 -NonMimeCharacterSet utf-8

The list of supported Charsets for Remote Domain- https://technet.microsoft.com/en-us/library/aa998600(v=exchg.150).aspx

In addition - A few tests showing how Outlook selects the encoding

There are 3 type of test: default (#1-4), with UTF-8 and disabled auto-selecting and UTF-8 (#5-10) and enabled auto-selecting (#11-16). So, if you disable "Auto-select encoding for outgoing message" UTF-8 will be used only for new emails (#5-8), and for reply emails Outlook will leave the original encoding (#9-10).

#	Outlook - Auto-select encoding for outgoing messages	Outlook - Encoding for outgoing messages	Email type (New, Reply)	Email format	Email text	Encoding
1	Yes	Western European (ISO)	New	html	English	Western European (ISO)
2	Yes	Western European (ISO)	New	html	Russian	KOI8-R
3	Yes	Western European (ISO)	New	html	Russian + Spec Symbols	UTF-8
4	Yes	Western European (ISO)	New	html	Russian + Italyan	KOI8-R
5	No	UTF-8	New	html	English	UTF-8
6	No	UTF-8	New	html	Russian	UTF-8
7	No	UTF-8	New	html	Russian + Spec Symbols	UTF-8
8	No	UTF-8	New	html	Russian + Italyan	UTF-8
9	No	UTF-8	Reply to Western European (ISO)	html	Russian	Western European (Windows)
10	No	UTF-8	Reply to KOI8-R	html	Russian	KOI8-R
11	Yes	UTF-8	New	html	English	UTF-8
12	Yes	UTF-8	New	html	Russian	UTF-8
13	Yes	UTF-8	New	html	Russian + Spec Symbols	UTF-8
14	Yes	UTF-8	New	html	Russian + Italyan	UTF-8
15	Yes	UTF-8	Reply to Western European (ISO)	html	Russian	UTF-8
16	Yes	UTF-8	Reply to KOI8-R	html	Russian	UTF-8