**Background**: I'm trying to set up a server to regularly pull RSS feeds, package them up in a mobi-ebook and send them to my kindle.

**Problem**: If I configure the server to send to my @kindle.com email address (as described here: https://www.amazon.com/gp/sendtokindle/email) I get back an email telling me: 
> Your email to Kindle(s) did not include any attachments.

I'm using the following command to send the email with attachment:

	echo "See attachment" | mail -s subject -aFrom:"$EMAIL_FROM" -A $EMAIL_FILE -r $EMAIL_FROM $EMAIL_TO

I tested this command by sending it to my personal email address instead of the @kindle.com one. The email appeared correctly with attachment in my personal inbox.

Interestingly it works fine (as in the ebook appears on my kindle) if I use mutt like this:

	echo "See attachment" | mutt -s subject -a $EMAIL_FILE -- $EMAIL_TO

I'm using postfix to forward the emails to a hosted smtp server. I already checked the postfix logs (`/var/log/mail.log`) but couldn't see any differences between the two methods above. The server is running Ubuntu 18.04.

**Question**: Why does it work with `mutt` but not with `mail`? How would I troubleshoot such an issue?

---

**Requested information**

The headers from mutt (Please let me know if I stripped out too much):

 Delivered-To: [...]
 Received: by 2002:a2e:9c0f:0:0:0:0:0 with SMTP id s15-v6csp1355528lji;
 Sat, 10 Nov 2018 10:47:03 -0800 (PST)
 [... removed X-* ...]
 [... removed ARC-* ...]
 Date: Sat, 10 Nov 2018 18:46:44 +0000
 From: [...]
 To: [...]
 Subject: mutt
 Message-ID: <20181110184643.GA23337@server>
 MIME-Version: 1.0
 Content-Type: multipart/mixed; boundary="5mCyUwZo2JvN/JJP"
 Content-Disposition: inline
 User-Agent: Mutt/1.9.4 (2018-02-28)
 [... removed X-* ...]
 
 --5mCyUwZo2JvN/JJP
 Content-Type: text/plain; charset=us-ascii
 Content-Disposition: inline
 
 See attachment
 
 --5mCyUwZo2JvN/JJP
 Content-Type: application/octet-stream
 Content-Disposition: attachment; filename="20181024T0942.mobi"
 Content-Transfer-Encoding: base64
 
 
 --5mCyUwZo2JvN/JJP--

Headers from mail:

 Delivered-To: [...]
 Received: by 2002:a2e:9c0f:0:0:0:0:0 with SMTP id s15-v6csp1355767lji;
 Sat, 10 Nov 2018 10:47:23 -0800 (PST)
 [... removed X-* ...]
 [... removed ARC-* ...]
 MIME-Version: 1.0
 Content-Type: application/octet-stream; name="20181024T0942.mobi"
 Content-Transfer-Encoding: base64
 Subject: mail
 To: [...]
 X-Mailer: mail (GNU Mailutils 3.4)
 Message-Id: <[email protected]>
 Date: Sat, 10 Nov 2018 18:47:07 +0000 (UTC)
 From: [...]
 [... removed X-* ...]

Upon closer inspection I noticed that the one from `mail` is missing the text "See attachment".

Versions:

 jonas@server:~$ mutt -v
 Mutt 1.9.4 (2018-02-28)
 Copyright (C) 1996-2016 Michael R. Elkins and others.
 Mutt comes with ABSOLUTELY NO WARRANTY; for details type `mutt -vv'.
 Mutt is free software, and you are welcome to redistribute it
 under certain conditions; type `mutt -vv' for details.
 
 System: Linux 4.15.0-34-generic (x86_64)
 ncurses: ncurses 6.1.20180127 (compiled with 6.1)
 libidn: 1.33 (compiled with 1.33)
 hcache backend: tokyocabinet 1.4.48
 [... removed mutt compiler info ...] 

 jonas@server:~$ mail --version
 mail (GNU Mailutils) 3.4
 Copyright (C) 2007-2017 Free Software Foundation, inc.
 License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
 This is free software: you are free to change and redistribute it.
 There is NO WARRANTY, to the extent permitted by law.
 
 jonas@server:~$ lsb_release -a
 No LSB modules are available.
 Distributor ID:	Ubuntu
 Description:	Ubuntu 18.04.1 LTS
 Release:	18.04
 Codename:	bionic

According to the man page on the server I'm using `-A` correctly:

 -A, --attach=FILE
 attach FILE

 -a, --append=HEADER: VALUE append given header to the message being sent