Fixes issue #2906 - Missing Content-Type header of parsed email fails processing.

app/models/channel/email_parser.rb

@@ -722,7 +722,7 @@ process unprocessable_mails (tmp/unprocessable_mail/*.eml) again
     end
 
     # e. g. Content-Type: video/quicktime
-    if filename.blank?
+    if filename.blank? && (content_type = headers_store['Content-Type'])
       map = {
         'message/delivery-status': %w[txt delivery-status],
         'text/plain':              %w[txt document],
@@ -734,7 +734,7 @@ process unprocessable_mails (tmp/unprocessable_mail/*.eml) again
         'image/gif':               %w[gif image],
       }
       map.each do |type, ext|
-        next if !headers_store['Content-Type'].match?(/^#{Regexp.quote(type)}/i)
+        next if !content_type.match?(/^#{Regexp.quote(type)}/i)
 
         filename = if headers_store['Content-Description'].present?
                      "#{headers_store['Content-Description']}.#{ext[0]}".to_s.force_encoding('utf-8')

test/data/mail/mail087.box

@@ -0,0 +1,27 @@
+To: support@example.com
+Subject: Failed Mail
+From: Test test@example.com
+Content-Type: multipart/mixed; boundary=earendil
+Message-Id: 20200123143934.05D7EE792E@example.com
+Date: Thu, 23 Jan 2020 15:39:33 +0100 (CET)
+MIME-Version: 1.0
+
+--earendil
+Content-Disposition: attachment; filename=fax_1234.pdf
+Content-Type: application/pdf; name=fax_+491234.pdf
+Content-Transfer-Encoding: base64
+
+JVBERi0xLjEgCiXi48/TCjEgMCBvYmoKPDwgCi9UeXBlIC9DYXRhbG9nIAovUGFnZXMgMyAwIFIg
+NjYzMzQ4NzM+XQo+PgpzdGFydHhyZWYKNDM4MjAzCiUlRU9GCg==
+
+--earendil
+Content-Transfer-Encoding: quoted-printable
+
+Sehr geehrter Kunde,
+
+Sie haben soeben ein neues Fax von +491234, fuer Rufnummer 01234=
+7 empfangen.
+
+Empfangszeit: Thursday, January 23 2020, at 03:39 PM
+Absender: +491234
+Empfaenger: 01234

test/data/mail/mail087.yml

@@ -0,0 +1,24 @@
+--- !ruby/hash:ActiveSupport::HashWithIndifferentAccess
+from: Test test@example.com
+from_email: Test test@example.com
+from_display_name: Test test@example.com
+to: support@example.com
+subject: Failed Mail
+body: no visible content
+content_type: text/plain
+attachments:
+- !ruby/hash:ActiveSupport::HashWithIndifferentAccess
+  data: !binary |-
+    JVBERi0xLjEgCiXi48/TCjEgMCBvYmoKPDwgCi9UeXBlIC9DYXRhbG9nIAovUGFnZXMgMyAwIFIgNjYzMzQ4NzM+XQo+PgpzdGFydHhyZWYKNDM4MjAzCiUlRU9GCg==
+  filename: fax_1234.pdf
+  preferences: !ruby/hash:ActiveSupport::HashWithIndifferentAccess
+    Content-Type: application/pdf; name=fax_+491234.pdf
+    Mime-Type: application/pdf
+    Charset: UTF-8
+- !ruby/hash:ActiveSupport::HashWithIndifferentAccess
+  data: "Sehr geehrter Kunde,\r\n\r\nSie haben soeben ein neues Fax von +491234, fuer
+    Rufnummer 012347 empfangen.\r\n\r\nEmpfangszeit: Thursday, January 23 2020, at
+    03:39 PM\r\nAbsender: +491234\r\nEmpfaenger: 01234\r\n"
+  filename: file
+  preferences: !ruby/hash:ActiveSupport::HashWithIndifferentAccess
+    Charset: UTF-8