SebastianKrupinski
commented
3 months ago Some possible mime structures...
multipart/mixed
text/plain, content-disposition=inline - A
multipart/mixed
multipart/alternative
multipart/mixed
text/plain, content-disposition=inline - B
image/jpeg, content-disposition=inline - C
text/plain, content-disposition=inline - D
multipart/related
text/html - E
image/jpeg - F
image/jpeg, content-disposition=attachment - G
application/x-excel - H
message/rfc822 - J
text/plain, content-disposition=inline - K
In this case, the above algorithm would decompose this to:
textBody => [ A, B, C, D, K ]
htmlBody => [ A, E, K ]
attachments => [ C, F, G, H, J ]
ivarsg
The purpose of this issue is to document known issues with our multipart and attachment handling.
Hidden attachments
Original report https://github.com/nextcloud/mail/issues/5282 and partly fixed by https://github.com/nextcloud/mail/pull/5339.
Sample eml
``` Return-Path:Message structure
```mermaid graph TD; multipart/mixed-->multipart/alternative; multipart/alternative-->text/html; multipart/alternative-->text/plain; multipart/mixed-->text/x-patch; ```Screenshots
Mail  Thunderbird HTML message Content-Disposition for text/x-patch is inline
Issue: We assume that mime parts with content-disposition = inline are referenced in via content-id / cid in the html document. Is the mime part not referenced, it's hidden.
Possible solutions: 1) Merge inlineAttachments and attachments like for text/plain emails. 2) If content-disposition = inline && content-id = null, then treat mime part as regular attachment.
Hidden message
Sample eml
``` Return-Path:Message structure
```mermaid graph TD; multipart/mixed-->text/html; multipart/mixed-->text/html; ```Screenshots
Mail  Thunderbird Multipart message with multiple text/html parts.
Issue: We show the first text/html part. Without looking at the source, you don't know there's something else.
Possible solutions: 1) Render both text/html parts 2) Add the mime parts as attachment