Disappearing attachments in Outlook 2007 with signed mails

[isento]

We have several user reported cases where attachments of emails disappeared on
the way to the recipient when the email message was signed with a verisign
certificate (Digital ID for Secure Email). Emails were sent as plain text and
without encryption. Attachment types vary (Office Documents, PDFs, Pictures).

Outlook 2003 shows the paper-clip to indicate attachments, but there is no file
available, neither in the preview nor in the normal view of the message. The
Scalix webmailer shows no attachment and no paper-clip.

We cannot reproduce the bug, but it still happens on a regular basis.

Setup (Sender):
- Outlook 2007 SP2
- MAPI 1.0.2536.0
- Windows XP SP3
- Scalix Connect 11.4.4.8866 (Build 176)
- Scalix Server 11.4.4.12886

[dougp23]

I encountered a similar problem last week. Turns out MS changed Outlook 2007 and how it sends messages, so if you send (compose) in HTML format, it causes a lot of grief for a lot of email clients including older Outlook versions. Solution: Compose in Plain Text. Attachments went through just fine.

[isento]

Thx you for this information. Are you sure that there is a correlation between the html-format and the disappearing attachments?

And aside from that, sending everything as plain-text is not an acceptable solution for our customer.

Our customers now also reported cases where attachments were lost with Outlook 2003 as sender.