The "MessageRetrievalMimeFormat" setting isn't honored for plain text-only email messages in IMAP in Exchange Server

Applies to: Exchange Server 2016 Enterprise EditionExchange Server 2016 Standard EditionExchange Server 2013 Enterprise More

Symptoms


When the value of the MessageRetrievalMimeFormat parameter is set to 1 or HtmlOnly by running the Set-IMAPSettings cmdlet, IMAP clients don't receive HTML messages for plain-text only emails in a Microsoft Exchange Server 2013 or Exchange Server 2016 environment.

Cause


This issue occurs because the MessageRetrievalMimeFormat parameter isn't honored during the Mime Convert process for plain-text only email messages.

Resolution


To fix this issue, install one of the following cumulative updates:

Status


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

References


Learn about the terminology that Microsoft uses to describe software updates.