Exchange 2016 - Issues with ECP/OWA after installing updates/KB

For several reasons after installation updates/KB (for example KB4536987) you may faced with some backfires. I collected 3 type of issues and their fixes.

Issue #1 - Lack os styles on ECP page

After authentication on ECP page you may see only text and hyperlinks without any images and styles.

How to fix

Run the script "C:\Program Files\Microsoft\Exchange Server\V15\Bin\UpdateCas.ps1" or do following manual steps:

• Go to "C:\Program Files\Microsoft\Exchange Server\V15\ClientAccess\ecp" folder and find the folder with latest version number of your server (e.g. "15.1.1913.7") and it will be empty.
• Open folder with previous version number (e.g. "15.1.1913.5") and copy all data to the new folder (e.g. "15.1.1913.7").
• Restart IIS. Reload the ECP page.

Exchange: How to reliably determine that a user is logged into mailbox?

Sometimes (for example while migration users are from another email system) there is a need for reliable determination that a user is logged into the mailbox (using Outlook or OWA).

The simplest answer is mailbox's lastlogontime (Get-MailboxStatistics). But it turnes out to be not quite true.
Attention! The attribute "LastLogonTime" of user's mailbox filled and updated when another user opens user's calendar.

Finally, I found 4 criterias which help to reliably determine that a user is logged into the mailbox.

1. "lastlogontime" (Get-MailboxStatistics) - necessary but not sufficient attribute.
2. "Languages" (Get-Mailbox) - this attribute filled when user entered into OWA and sometimes filled when entered into Outlook.
3. "WorkingHoursTimeZone" (Get-MailboxCalendarConfiguration) - this attribute filled when user entered into OWA and sometimes filled when entered into Outlook. Deffault value - "Pacific Standard Time", so you can use it only if users are in a different time zone.
4. "Quick Step Settings" (Get-MailboxFolderStatistics) - this is not an attribute, it is a checking for the presence of a folder "Quick Step Settings" in the mailbox, because it appears only when you open/configure Outlook.

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.

Microsoft Exchange 2016 and OwaVersion:Exchange2013

During the study of Exchange 2016 RTM I noticed one thing - "OwaVersion" of OWA Virtual Directory is "Exchange2013". CU1 - CU14 still no changed it.

[PS] C:\Windows\system32>Get-ExchangeServer | fl AdminDisplayVersion
AdminDisplayVersion : Version 15.1 (Build 466.34)

[PS] C:\Windows\system32>Get-OwaVirtualDirectory | fl OWAVersion
OwaVersion : Exchange2013