Fix content filtering of builds@lucene.apache.org to accept all content types

I open this issue because a week ago we tried to fix the issue with INFRA Chat, but with no success.

The problem is the following: We tried to redirect Jenkins eMails to the new mailing list builds@lucene.apache.org (as a test only for https://jenkins.thetaphi.de, but ASF jenkins and another one including those from Elasticsearch will also be switched). Unfortunately the mails are completely swallowed since now 2 weeks. The initial Jenkins-test mails were successfully delivered and the moderation was used to allow posts from jenkins@thetaphi.de to post to list.

All mails sent to the builds list are swallowed and don't even appear on the moderation queue. We have no idea where they are lost.

[~humbedooh] tried to allow HTML mails, but that did not help.

Please change the configuration of the builds@lucene.a.o list to accept all content types including attachments. Once a few mails went through, we can try to reduce it again. But as nobody except the build servers will send mails I see no issue to remove mail filtering at all.

More infos:
- Analyzing a mail previously sent to dev@lucene.apache.org shows that jenkins uses multipart/mixed and UTF-8 encoding: Analyzing a mail from jenkins looks like it uses multipart/mixed format: https://lists.apache.org/api/source.lua/d415bf5c26db9aaaa1ab17a2b92f664728de9927cd788fc07afd8fd3@%3Cdev.lucene.apache.org%3E
- dev@lucene.apache.org always accepted mails by all of our jenkins servers, so maybe just copy the filter config from there
- Daniel Gruno also told me that mails are *not* stuck in spam!
- The envelope sender is static so no dynamic parts (it's a standard postfix sending those mails listed under SPF with those IPs represented by this hostname: mailout.sd-datasolutions.de)

Here is the last recent 2 mails sent:

Sep 11 05:04:32 serv1 postfix/smtpd[16229]: connect from ip6-localhost[::1]
Sep 11 05:04:32 serv1 postfix/smtpd[16229]: 335651080E4C: client=ip6-localhost[::1]
Sep 11 05:04:32 serv1 postfix/cleanup[16232]: 335651080E4C: message-id=<361586855.135.1568178272211.JavaMail.jenkins@serv1.sd-datasolutions.de>
Sep 11 05:04:32 serv1 postfix/qmgr[1633]: 335651080E4C: from=<jenkins@thetaphi.de>, size=106077, nrcpt=1 (queue active)
Sep 11 05:04:32 serv1 postfix/smtpd[16229]: disconnect from ip6-localhost[::1] ehlo=1 mail=1 rcpt=1 data=1 quit=1 commands=5
Sep 11 05:04:40 serv1 postfix/smtp[16233]: 335651080E4C: to=<builds@lucene.apache.org>, relay=mx1-he-de.apache.org[2a01:4f8:c2c:2bf7::1]:25, delay=8, delays=0.08/0/6.9/1, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as 3160B7DD32)
Sep 11 05:04:40 serv1 postfix/qmgr[1633]: 335651080E4C: removed
Sep 11 07:45:04 serv1 postfix/smtpd[16559]: connect from ip6-localhost[::1]
Sep 11 07:45:04 serv1 postfix/smtpd[16559]: EAC7F1080267: client=ip6-localhost[::1]
Sep 11 07:45:04 serv1 postfix/cleanup[16562]: EAC7F1080267: message-id=<1118066408.137.1568187904963.JavaMail.jenkins@serv1.sd-datasolutions.de>
Sep 11 07:45:05 serv1 postfix/qmgr[1633]: EAC7F1080267: from=<jenkins@thetaphi.de>, size=104998, nrcpt=1 (queue active)
Sep 11 07:45:05 serv1 postfix/smtpd[16559]: disconnect from ip6-localhost[::1] ehlo=1 mail=1 rcpt=1 data=1 quit=1 commands=5
Sep 11 07:45:13 serv1 postfix/smtp[16566]: EAC7F1080267: to=<builds@lucene.apache.org>, relay=mx1-ec2-va.apache.org[34.199.147.133]:25, delay=8.2, delays=0.09/0.01/7/1.1, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as B539FBC686)
Sep 11 07:45:13 serv1 postfix/qmgr[1633]: EAC7F1080267: removed