From MozillaZine Knowledge Base
- This article was written for Thunderbird but also applies to Mozilla Suite / SeaMonkey (though some menu sequences may differ).
By default, Thunderbird and SeaMonkey forward the message as an ".eml" attachment, where the name is derived from the subject line (see bugs 220646 and 380354 for a discussion on this). It doesn't copy the message into the new message, and the forwarded message cannot be edited. Thunderbird has changed the default to "inline" with version 3.0, which copies the content of the original message into your own message, thus it can be edited as necessary.
- Certain e-mail clients, e.g., webmail interfaces as well as command-line clients like PINE and Mutt tend to have problems with displaying such ".eml" attachments.
- Many internet service providers block attachments with specific suffixes that are known to potentially contain viruses. This frequently includes ".eml" attachments. Thus, these attachments may be removed or the complete e-mail discarded.
- If you do not see messages that you received as ".eml" attachment, make sure to have View → Display Attachments Inline checked.
- Send your e-mails inline rather than as an attachment: In Thunderbird, click on Tools → Options. Select the Composition category and the General tab. Select "Inline" from the drop-down box next to Forward Messages. In SeaMonkey, this setting can be found in the Edit → Preferences → Mail & Newsgroups → Composition tab.
- If the e-mail is still not readable, use plain text and disable HTML.
- If you have to forward a message as attachment, compose a message as usual and then drag-and-drop the message to be forwarded from the thread pane into the attachment box. This will give it a fixed file name of "Attached Message" without ".eml" suffix, which should pass ISP filtering.
- While forwarding inline in many cases works better than forwarding as attachment, HTML messages received in a certain encoding may not include images that were part of the original message when forwarded inline. In those cases, using Reply rather than Forward frequently retains the complete message, including images. Don't forget to replace the e-mail address of the original sender by the intended recipients though.
- To include the contents of all visible (inlined) attachments in the reply quote, make sure to set the mail.reply_quote_inline preferences in the Config Editor. Otherwise, only the content of the main message will be quoted. Any non-inlined attachments you want to forward can be reattached by drag-and-drop from the original message into the attachment pane of the message you compose.
- Forwarding an e-mail which contains another message forwarded to you "as attachment" will just reattach that message even if you forward inline. Using Reply instead of Forward and replacing the original sender with your recipients helps here as well, since it collects all text and image contents even from deeper nested message attachments and forms a single quote used for your reply. Other attachments may have to be manually reattached (e.g., by drag and drop from the original message).
- Bug 220646 – Forward as attachment: Attachment name is subject, without ".eml" extension
- Bug 230448 – Change default forwarding preference to inline instead of attachment
- Bug 269826 – Problems related to message/rfc822 attachment (forwarded mail) in a mail and ".eml" file
- Bug 307023 – Re-editing quoted-printable HTML message shows corruption of tag attributes
- Bug 312025 – Filter action Forward Message to sends the mail as attachment regardless of option
- Bug 380354 – TB2 adds ".eml" extension to attached messages, causes virus scanner to complain; TB1.5 was OK
- The ForwardAs extension adds a submenu to the Forward button that lets you choose between forwarding inline or as an attachment.
- The Forward extension also adds an item to select between inline and attachment to the context menu.
- The NotTo extension adds a NotTo Forward command to the Forward button that prevents the message being sent to the original sender.