Email standards Beginning with the text-based
Unix Mail command, email traditionally used the inline or bottom
posting styles when replying to messages. Outlook Express, as well as
Lotus Notes and Microsoft Outlook, top-post (show replies newest to oldest) by default. Microsoft Outlook and Microsoft Exchange use a
proprietary email attachment format called
Transport Neutral Encapsulation Format (TNEF) to handle formatting and other features specific to Outlook such as meeting requests. Outlook Express and other email clients are unable to read this format. This can be confusing to Outlook Express users (as well as those who use other email clients) who receive attachments sent from Outlook.
Database corruption Outlook Express has been prone to a number of problems which can corrupt its files database, especially when the database increases in size due to an increasing number of stored emails and during database compaction. This has led to a thriving market for software that can back up, restore and recover corrupted files. An open-source project called UnDBX was also created, which seems to be successful in recovering corrupt databases. Microsoft has also released documentation which may be able to correct some non-severe problems and restore access to email messages, without resorting to third-party solutions.
Security issues Outlook Express was one of the earlier email clients to support
HTML email and scripts. As a result, emails were commonly infected with
viruses. Previously, another security flaw was that a
script could automatically be opened as an
attachment. Another bug was in Outlook Express's attachment handling that allowed an executable to appear to be a harmless attachment such as a graphics file. Opening or previewing the email could cause code to run without the user's knowledge or consent. Outlook Express uses Internet Explorer to render HTML email.
Internet Explorer has been subjected to many security vulnerabilities and concerns. With Outlook Express SP2 (part of Windows XP SP2), Microsoft has tried to correct the security holes. Outlook Express now blocks images inside emails by default. It uses only the restricted security zone for HTML email, which disables scripts and imposes restrictions on what web content can be rendered. It also warns when opening potentially malicious attachments.
Handling of PGP/MIME signed messages Outlook Express does not correctly handle
MIME, and will not display the body of signed messages inline. Users get a filled email and one attachment (one of the message text and one of the signature) and therefore need to open an attachment to see the email. If the email has been
forwarded several times, users need to open attached email messages one inside the other multiple times to reach the parent email message. This bug has still not been rectified. The proper behavior is described in RFC 1847. When replying or forwarding a message to a user who has a digital signature, Outlook Express gives an error and does not allow the user to continue if there is no digital signature installed for the sender.
Extensibility Outlook Express does not have a documented
object model like Microsoft Outlook. Programmatic access to, or control of Outlook Express for custom messaging applications or plugins is not officially documented or supported by Microsoft. IStoreNamespace and IStoreFolder interfaces were documented in 2003, but they are only related to the storage. Some companies have managed to create their plugins hacking the interface using Windows
hooks. A significant one was the
PGP plugin because it was the only example of a working plugin whose
source code was available (licensed under
GPL). By 2003, some companies provided commercial solutions to develop add-ins.
Office 2007 spell checker incompatibility Outlook Express did not have a dedicated spell checker. It used the spell checkers from
Microsoft Office if Office was also installed. However, the
Office 2007 spell checkers, except for the French spell checker, were incompatible with Outlook Express. Microsoft acknowledged this problem, but did not provide any sort of remedy. There were third party files that fixed the issue, but Microsoft never took action.
Glitches and other unusual aspects Cancelling sending an email while it is being sent would not effectively prevent it from being sent. Similarly, when importing
.PST files, cancelling the import while it was in progress merely canceled the import of the current folder and the import resumed with the next folder. Furthermore, Outlook Express only supported .dbx files that were smaller than 2 GB, and had performance problems when dealing with files approaching that limit. ==See also==