Why there is no support for emails with `Content-Transfer-Encoding: 7bit`

[mukul-brevo]

Is your feature request related to a problem? Please describe.

I tried parsing an eml with Content-Transfer-Encoding: 7bit But seems like only base64 and quoted-printable are supported as per the logic here

Error

❯ go run .
err: failed to parse EML contents: failed to parse EML body parts: failed to parse multipart body: unsupported Content-Transfer-Encoding

Below the snippet i used

func main() {
    msg, err := gomail.EMLToMsgFromFile("./eml.txt")
    if err != nil {
        fmt.Println("err:", err)
    }
    files := msg.GetAttachments()
    for _, file := range files {
        fmt.Println(file)
    }
}

eml.txt

FCC: imap://piro-test@mail.clear-code.com/Sent
X-Identity-Key: id1
X-Account-Key: account1
From: "piro-test@clear-code.com" <piro-test@clear-code.com>
Subject: test confirmation
To: piro.outsider.reflex+1@gmail.com, piro.outsider.reflex+2@gmail.com,
 mailmaster@example.com, mailmaster@example.org, webmaster@example.com,
 webmaster@example.org, webmaster@example.jp, mailmaster@example.jp
Message-ID: <05c18622-f2ad-cb77-2ce9-a0bbfc7d7ad0@clear-code.com>
Date: Thu, 15 Aug 2019 14:54:37 +0900
X-Mozilla-Draft-Info: internal/draft; vcard=0; receipt=0; DSN=0; uuencode=0;
 attachmentreminder=0; deliveryformat=4
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:69.0) Gecko/20100101
 Thunderbird/69.0
MIME-Version: 1.0
Content-Type: multipart/mixed;
 boundary="------------26A45336F6C6196BD8BBA2A2"
Content-Language: en-US

This is a multi-part message in MIME format.
--------------26A45336F6C6196BD8BBA2A2
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit

testtest
testtest
testtest
testtest
testtest
testtest

--------------26A45336F6C6196BD8BBA2A2
Content-Type: text/plain; charset=UTF-8;
 name="sha1hash.txt"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
 filename="sha1hash.txt"

NzRjOGYwOWRmYTMwZWFjY2ZiMzkyYjEzMjMxNGZjNmI5NzhmMzI1YSAqZmxleC1jb25maXJt
LW1haWwuMS4xMC4wLnhwaQpjY2VlNGI0YWE0N2Y1MTNhYmNlMzQyY2UxZTJlYzJmZDk2MDBl
MzFiICpmbGV4LWNvbmZpcm0tbWFpbC4xLjExLjAueHBpCjA3MWU5ZTM3OGFkMDE3OWJmYWRi
MWJkYzY1MGE0OTQ1NGQyMDRhODMgKmZsZXgtY29uZmlybS1tYWlsLjEuMTIuMC54cGkKOWQ3
YWExNTM0MThlYThmYmM4YmU3YmE2ZjU0Y2U4YTFjYjdlZTQ2OCAqZmxleC1jb25maXJtLW1h
aWwuMS45LjkueHBpCjgxNjg1NjNjYjI3NmVhNGY5YTJiNjMwYjlhMjA3ZDkwZmIxMTg1NmUg
KmZsZXgtY29uZmlybS1tYWlsLnhwaQo=
--------------26A45336F6C6196BD8BBA2A2
Content-Type: application/json;
 name="manifest.json"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
 filename="manifest.json"
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--------------26A45336F6C6196BD8BBA2A2--

Describe the solution you'd like

Is there any special reason for it, or are there any plans to add it in future?

Describe alternatives you've considered

No response

Additional context

No response

[wneessen]

Hi @mukul-brevo, thanks for opening the issue. This is an oversight. 7bit is not that commen anymore, and I simply overlooked the posilibty. I'll add support soon.