6 Appendix A: Product Behavior

  • Article

The information in this specification is applicable to the following Microsoft products or supplemental software. References to product versions include updates to those products.

  • Microsoft Exchange Server 2003

  • Microsoft Exchange Server 2007

  • Microsoft Exchange Server 2010

  • Microsoft Exchange Server 2013

  • Microsoft Exchange Server 2016

  • Microsoft Exchange Server 2019

  • Microsoft Office Outlook 2003

  • Microsoft Office Outlook 2007

  • Microsoft Outlook 2010

  • Microsoft Outlook 2013

  • Microsoft Outlook 2016

  • Microsoft Outlook 2019

  • Microsoft Outlook 2021

  • Microsoft Outlook 2024 Preview

Exceptions, if any, are noted in this section. If an update version, service pack or Knowledge Base (KB) number appears with a product name, the behavior changed in that update. The new behavior also applies to subsequent updates unless otherwise specified. If a product edition appears with the product version, behavior is different in that product edition.

Unless otherwise specified, any statement of optional behavior in this specification that is prescribed using the terms "SHOULD" or "SHOULD NOT" implies product behavior in accordance with the SHOULD or SHOULD NOT prescription. Unless otherwise specified, the term "MAY" implies that the product does not follow the prescription.

<1> Section 1.3: POP3 servers support at least one authentication mechanism. Office Outlook 2003 supports USER and PASS verbs, as defined in [RFC1939]. Office Outlook 2007 supports the AUTH verb, as defined in [RFC1734]. Office Outlook 2003 and Office Outlook 2007 do not support the APOP command, as specified in [RFC1939] section 7. Both Office Outlook 2003 and Office Outlook 2007 support AUTH NTLM.

<2> Section 3.2.5.3: In Exchange 2003, messages received by using MAPI are converted to MIME the first time they are retrieved and subsequently stored. The MIME size can be different before the message is retrieved than after it is converted to MIME. This is necessary because NTLM messages contain data outside the ASCII character range, whereas POP3 supports only ASCII characters.

<3> Section 3.2.5.3: In Exchange 2003, the MIME stream is preserved. In Exchange 2007, Exchange 2010, Exchange 2013, Exchange 2016, and Exchange 2019 the MIME stream is not preserved. Only content of the best body as specified in [MS-OXBBODY] is preserved. The order in which the best body part is selected is as follows:

  1. Enriched Text Format

  2. HTML

  3. Plain text

Therefore, the MIME stream is regenerated every time a message is retrieved. The alternative body parts are regenerated on demand as the message is retrieved. In Exchange 2010, the MIME headers and body parts of messages are stored if the headers existed when the messages were delivered. In Microsoft Exchange Server 2010 Service Pack 1 (SP1), Exchange 2013, Exchange 2016, andExchange 2019, messages are not stored in MIME format. Messages are converted from MAPI to MIME before being sent to the client. When the client requests the size of a message before retrieving the actual message itself, the MIME size provided is the size associated with the message as a MAPI property. When the client retrieves the message, the message is converted from MAPI to MIME, and the message size calculated thereafter can be different from the size calculated from the MAPI property. Additionally, if the message is modified by MAPI, the size is likely to change again, as is the corresponding MIME size after actual conversion from MAPI to MIME.