Bugzilla

Is it possible that the inline .jpg images are external links? If so, there's a setting at yahoo under "Viewing email" => "Show images in messages" that may affect how yahoo imap sends messages to clients like tb. Try setting it is set to "Always except in spam folder" and see if that helps if your .jpgs are links.. This shouldn't affect messages with the .jpg bytes directly embedded in the email.  Anyhow, just a possibility.

I've been able to create a message like you describe (text/jpg/text/jpg/text...) in yahoo Drafts but when I copy it to a regular yahoo folder, tb only displays partial images. So not sure what's going on. 
But if I copy it to a non-yahoo server like dovecot, it displays OK in tb. So I'm pretty sure yahoo is doing something it shouldn't like Looks like only returning a partial fetch for this too.

Is it possible that the inline .jpg images are external links? If so, there's a setting at yahoo under "Viewing email" => "Show images in messages" that may affect how yahoo imap sends messages to clients like tb. Try setting it to "Always except in spam folder" and see if that helps if your .jpgs are links. This shouldn't affect messages with the .jpg bytes directly embedded in the email.  Anyhow, just a possibility.

I've been able to create a message like you describe (text/jpg/text/jpg/text...) in yahoo Drafts but when I copy it to a regular yahoo folder, tb only displays partial images. So not sure what's going on. 
But if I copy it to a non-yahoo server like dovecot, it displays OK in tb. So I'm pretty sure yahoo is doing something it shouldn't. Looks like it's only returning a partial fetch for this too. So my guess right now is this and bug 1821755 are dupes.