Issue export to email: Emails are flagged as spam
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### Summary
When launching issue export, an email is generated. Unfortunately the email is detected as spam by SpamAssasin.
### Steps to reproduce
This is the spam detection header:
```
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on host.com
X-Spam-Flag: YES
X-Spam-Level: *******
X-Spam-Status: Yes, score=7.2 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,
DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,HTML_MESSAGE,
J_CHICKENPOX_24,J_CHICKENPOX_34,J_CHICKENPOX_44,J_CHICKENPOX_45,
J_CHICKENPOX_47,J_CHICKENPOX_48,J_CHICKENPOX_54,J_CHICKENPOX_64,
J_CHICKENPOX_66,J_CHICKENPOX_74,J_CHICKENPOX_84,RM_bw_Generic,SURBL_BLOCKED,
TW_JS,TW_MK,WEIRD_QUOTING autolearn=disabled version=3.4.0
X-Spam-Report:
* 0.0 SURBL_BLOCKED ADMINISTRATOR NOTICE: The query to SURBL was blocked.
* See http://wiki.apache.org/spamassassin/DnsBlocklists#dnsbl-block
* for more information.
* [URIs: gitlab.com]
* 0.2 HEADER_FROM_DIFFERENT_DOMAINS From and EnvelopeFrom 2nd level mail
* domains are different
* 0.1 TW_MK BODY: Odd Letter Triples with MK
* 0.6 J_CHICKENPOX_47 BODY: 4alpha-pock-7alpha
* 0.0 WEIRD_QUOTING BODY: Weird repeated double-quotation marks
* 0.6 J_CHICKENPOX_54 BODY: 5alpha-pock-4alpha
* 0.6 J_CHICKENPOX_44 BODY: 4alpha-pock-4alpha
* 0.6 J_CHICKENPOX_24 BODY: 2alpha-pock-4alpha
* 0.6 J_CHICKENPOX_45 BODY: 4alpha-pock-5alpha
* 0.6 J_CHICKENPOX_34 BODY: 3alpha-pock-4alpha
* 0.3 RM_bw_Generic BODY: Body mentions a generic product of some kind
* 0.6 J_CHICKENPOX_66 BODY: 6alpha-pock-6alpha
* 0.6 J_CHICKENPOX_84 BODY: 8alpha-pock-4alpha
* 0.6 J_CHICKENPOX_48 BODY: 4alpha-pock-8alpha
* 0.1 TW_JS BODY: Odd Letter Triples with JS
* 0.6 J_CHICKENPOX_64 BODY: 6alpha-pock-4alpha
* 0.6 J_CHICKENPOX_74 BODY: 7alpha-pock-4alpha
* 0.0 HTML_MESSAGE BODY: HTML included in message
* -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's
* domain
* 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily
* valid
* -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature
* 0.0 DKIMWL_WL_HIGH DKIMwl.org - Whitelisted High sender
```
The (anonymized) email can be downloaded here: [issue-export-mail-reported-as-spam.eml](/uploads/fb1edb4261e8e068790a9edd57ff19e1/issue-export-mail-reported-as-spam.eml)
issue