Knowledge Base

Messages from Apple devices and mobile devices are sent in plain text


A message sent from an Apple device (iPhone, iPad, Mac, etc.) or a mobile device (e.g. based on Android) is sent in the plain text format. As a result, the signature added by CodeTwo software to this message does not look as expected (Fig. 1.) or is not added at all (if you have not configured the template for the plain text format). In some scenarios, messages previously converted to the HTML format are rolling back to the plain text format.

HTML vs plain text in a mobile email signature.
Fig. 1. HTML vs plain text in a mobile email signature.


This problem is related to the default behavior in these devices:

  • Most mobile devices use plain text as their default format. Often, there is no option to set the message format (plain text / RTF / HTML) before sending it.
  • In the case of Apple Mail, when you reply, forward or compose new messages on a Mac, this mail client automatically uses the plain text or HTML format. Unfortunately, even if you set the default mail composition format to Rich Text in the application's preferences, it does not always work: creating a message without any text formatting results in Apple Mail using plain text regardless of the program's settings and the original message format. Such behavior has also been observed in earlier versions of Mac OS X.


The naming convention in Apple devices does not entirely meet the one used by Microsoft. While Microsoft refers to Rich Text as a separate document format (RTF), in the Apple Mail app Rich Text means HTML (Apple devices are not able to send messages directly in the Microsoft’s RTF format).

If you want to have HTML signatures added to Apple devices and mobile devices, you can force email format conversion:

Forcing email format in CodeTwo Exchange Rules Pro

To force an email format in CodeTwo Exchange Rules Pro, you need to:

  1. Open the software's Administration Panel. In this scenario we will force all messages to be converted to the HTML format.
  2. Create a new rule or edit an existing one.
  3. Ensure that this rule is at the top of the rules list.
  4. If necessary, configure the rule's conditions and exceptions. If you skip this step, the rule will apply to all emails.
  5. On the Actions tab, add a new action and choose Force email format (Fig. 2.). Configure the action to convert messages to HTML. For more information, see the user's manual.
  6. Go to the Options tab and select Go to the next rule in both scenarios (both when the rule is and is not applied).

Forcing the HTML format in CodeTwo Exchange Rules Pro.
Fig. 2. Forcing the HTML format in CodeTwo Exchange Rules Pro.

Forcing email format in Microsoft Exchange Server

Open the Exchange Management Shell, wait until the console connects to your server and execute the following command:

set-remotedomain -Identity Default -ContentType MimeHtml

Note that this cmdlet sets the HTML format as preferred on your Exchange. However, it will not cause automatic conversion of the plain text format to HTML. If you would like to allow a client-based choice or force plain text, see our Knowledge Base article.

Changing the default message format to HTML in Apple Mail

  1. Open the Mail app on your Mac.
  2. On the top menu, click Mail and then Preferences.
  3. Switch to the Composing section (Fig. 3.).
  4. Set Message Format to Rich Text.
  5. Start composing a new message and apply some formatting at least once (it is enough to just bold some text).
  6. Send the message.

Composing preferences in Apple Mail.
Fig. 3. Composing preferences in Apple Mail.

The message should be sent in HTML and stamped with the HTML version of your signature (assuming that the HTML signature template was correctly configured in your CodeTwo software).

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