First shot at replacing Devise mails with plaintext mails.

app/views/devise_mailer/confirmation_instructions.text.erb

@@ -0,0 +1,13 @@
+= "#{t('common.text.hello')} #{@resource.nickname},"
+
+= t('devise.confirmation.email.text')
+
+= t('devise.confirmation.email.link')
+
+= confirmation_url(@resource, confirmation_token: @token)
+
+= t('devise.reset.ignoremail_begin')
+= t('devise.reset.ignoremail_addr')
+= t('devise.reset.ignoremail_end')
+
+= render 'shared/email/imprint'

app/views/devise_mailer/welcome_mail.text.erb

@@ -0,0 +1,18 @@
+<%# Copyright (c) 2012-2016, Fairmondo eG.  This file is
+    licensed under the GNU Affero General Public License version 3 or later.
+    See the COPYRIGHT file for details. %>
+
+<%= "#{t('common.text.hello')} #{@resource.nickname}," %>
+
+<%= t('devise.confirmation.text') %>
+<% if @resource.newsletter %>
+<%= t('devise.confirmation.link_if_newsletter') %>
+<%= confirmation_url(@resource, confirmation_token: @token) %>
+<% else %>
+<%= t('devise.confirmation.link') %>
+<%= confirmation_url(@resource, confirmation_token: @token) %>
+<% end %>
+
+<%= t('devise.confirmation.ignoremail') %>
+
+<%= render 'shared/email/imprint' %>

app/views/shared/email/_imprint.text.erb

@@ -0,0 +1,15 @@
+--
+Fairmondo eG
+Glogauer Str. 21
+10999 Berlin
+
+www.fairmondo.de
+Gutes einfach entdecken
+
+Registergericht: Amtsgericht Berlin-Charlottenburg, GnR 738 B  USt-IdNr.: DE 290376380
+
+Vorstand: Felix Weth, Richard Schmid
+Aufsichtsratsvorsitzender: Kim Stattaus
+
+Facebook: www.facebook.com/fairmondo
+Beteiligung an der Genossenschaft: mitmachen.fairmondo.de/anteile-zeichnen/