如何使用 Python MIME multipart 分离 email？

Question

Sending an email using sockets. I want to separate plain text and attachment. I use MIME multipart/mixed; boundary.

cSockSSL.send("MIME-Version: 1.0\r\n".encode())
cSockSSL.send("Content-Type: multipart/mixed; boundary=gg4g5gg\r\n".encode())
cSockSSL.send("--gg4g5gg".encode('ascii'))

cSockSSL.send("Content-Type: text/plain\r\n".encode())
cSockSSL.send("Some text".encode())
cSockSSL.send("--gg4g5gg".encode())

cSockSSL.send("Content-Type: text/plain\r\n".encode())
cSockSSL.send("Content-Disposition: attachment; filename = gg.txt\r\n".encode())
cSockSSL.send(txt_file)
cSockSSL.send("--gg4g5gg--".encode())
cSockSSL.send("\r\n.\r\n".encode())

In this case, I get an empty email with the header. If I delete first boundary I'll get this:

Some text--gg4g5ggContent-Type: text/plain Content-Disposition: attachment; filename = gg.txt Hey! I'm txt file!--gg4g5gg--

How to correctly split content-type?

Answer 1

Your email data is malformed, as you are missing several required line breaks.

Per RFC 2822 , you need to separate the email's headers from the email's body using \r\n\r\n instead of \r\n .

And per RFC 2045 , you need to separate MIME headers from MIME bodies using \r\n\r\n instead of \r\n . And, you are missing \r\n in front of each MIME boundary that follows a text body, and after each MIME boundary.

So, essentially, you are sending an email that looks like this, all squished together:

MIME-Version: 1.0
Content-Type: multipart/mixed; boundary=gg4g5gg
--gg4g5ggContent-Type: text/plain
Some text--gg4g5ggContent-Type: text/plain
Content-Disposition: attachment; filename = gg.txt
<txt_file>--gg4g5gg--
.

But it needs to look more like this instead:

MIME-Version: 1.0
Content-Type: multipart/mixed; boundary=gg4g5gg

--gg4g5gg
Content-Type: text/plain

Some text
--gg4g5gg
Content-Type: text/plain
Content-Disposition: attachment; filename = gg.txt

<txt_file>
--gg4g5gg--
.

So, try this instead:

cSockSSL.send("DATA\r\n".encode())
# verify response is 354...

cSockSSL.send("MIME-Version: 1.0\r\n".encode())
cSockSSL.send("Content-Type: multipart/mixed; boundary=gg4g5gg\r\n".encode())
cSockSSL.send("\r\n".encode()) # add a line break

cSockSSL.send("--gg4g5gg\r\n".encode('ascii')) # add a line break
cSockSSL.send("Content-Type: text/plain\r\n".encode())
cSockSSL.send("\r\n".encode()) # add a line break
cSockSSL.send("Some text".encode())

cSockSSL.send("\r\n--gg4g5gg\r\n".encode()) # add line breaks
cSockSSL.send("Content-Type: text/plain\r\n".encode())
cSockSSL.send("Content-Disposition: attachment; filename=gg.txt\r\n".encode())
cSockSSL.send("\r\n".encode()) # add a line break
cSockSSL.send(txt_file)
cSockSSL.send("\r\n--gg4g5gg--\r\n".encode()) # add line breaks

cSockSSL.send(".\r\n".encode())

Something else to be aware of - because the DATA command terminator is .\r\n , if "Some text" or txt_file contain any lines that begin with the . character, you MUST escape each leading . as .. , per RFC 2821 Section 4.5.2 .

I suggest you study the RFCs mentioned above more carefully.