some contact form messages not being sent by email

Problem

83 people have filled in the form and had their responses stored in Perch. 2 of these responses (sent on 5th and 19th August) have not been sent on to the site owner by email (they are stored in Perch).

I've checked the client's email account and they have not gone to the spam folder. Looking in Perch there doesn't seem to be anything different about the content in these two entries. I'm wondering if it is something with the hosting rather than Perch causing the problem. The host is looking into it for me.

Setup

I have a multilingual site that has two forms with the same ID (same fields in each form but the labels have different text for each language) so that both sets of responses appear under the same form in the Perch admin. If I send test messages from each language side they both appear in Perch and get sent on by email. This site has Perch 2.4.9 with Forms 1.7 (I know a little out of date but don't want to add in interface changes with Assets for this client just yet).

Form Templates

English

<h2><perch:content id="heading" type="text" label="Heading" required="true"/></h2>

<perch:content id="intro" type="textarea" label="Intro" markdown="true" size="m" required="true"/>

<h2>Online Form</h2>

<p>Fill in the online form and we will get back to you as soon as possible.</p>

<perch:form id="contact" method="post" app="perch_forms">
  <div>
    <perch:label for="name">Name<span class="form__required">*</span></perch:label>
    <perch:input type="text" id="name" required="true" label="Name" />
    <perch:error for="name" type="required">
      <p class="form__error">enter your name</p>
    </perch:error>
  </div>

  <div>
    <perch:label for="email">Email<span class="form__required">*</span></perch:label>
    <perch:input type="email" id="email" required="true" label="Email" />
    <perch:error for="email" type="required">
      <p class="form__error">enter your email address</p>
    </perch:error>
    <perch:error for="email" type="format">
      <p class="form__error">enter a valid email address</p>
    </perch:error>
  </div>

  <div>
    <perch:label for="phone">Phone Number</perch:label>
    <perch:input type="text" id="phone" label="Phone Number" />
  </div>

  <div>
    <perch:label for="message">Message<span class="form__required">*</span></perch:label>
    <perch:input type="textarea" id="message" required="true" label="Message" />
    <perch:error for="message" type="required">
      <p class="form__error">enter your message</p>
    </perch:error>
  </div>

  <div>
    <perch:input type="submit" id="submit" value="Send Message" />
  </div>

  <perch:success>
    <p class="form__success"><perch:content id="success" type="text" label="Thank you message" size="xl" required="true"/></p>
  </perch:success>
</perch:form>

French

<h2><perch:content id="heading" type="text" label="Heading" required="true"/></h2>

<perch:content id="intro" type="textarea" label="Intro" markdown="true" size="m" required="true"/>

<h2>Formulaire en ligne</h2>

<p>Remplissez le formulaire en ligne et nous vous répondrons dès que possible.</p>

<perch:form id="contact" method="post" app="perch_forms">
  <div>
    <perch:label for="name">Nom<span class="form__required">*</span></perch:label>
    <perch:input type="text" id="name" required="true" label="Name" />
    <perch:error for="name" type="required">
      <p class="form__error">saisissez votre nom</p>
    </perch:error>
  </div>

  <div>
    <perch:label for="email">Email<span class="form__required">*</span></perch:label>
    <perch:input type="email" id="email" required="true" label="Email" />
    <perch:error for="email" type="required">
      <p class="form__error">saisissez votre adresse email</p>
    </perch:error>
    <perch:error for="email" type="format">
      <p class="form__error">saisissez une adresse email valide</p>
    </perch:error>
  </div>

  <div>
    <perch:label for="phone">Numéro de téléphone</perch:label>
    <perch:input type="text" id="phone" label="Phone Number" />
  </div>

  <div>
    <perch:label for="message">Message<span class="form__required">*</span></perch:label>
    <perch:input type="textarea" id="message" required="true" label="Message" />
    <perch:error for="message" type="required">
      <p class="form__error">saisissez votre message</p>
    </perch:error>
  </div>

  <div>
    <perch:input type="submit" id="submit" value="Envoyez votre message" />
  </div>

  <perch:success>
    <p class="form__success"><perch:content id="success" type="text" label="Thank you message" size="xl" required="true"/></p>
  </perch:success>
</perch:form>

Diagnostics

PERCH INFORMATION

Perch: 2.4.9
Production mode: Production (100)
Installed apps: content (2.4.9), perch_forms (1.7), perch_backup (1.2)
DB driver: PDO
DB tables: perch2_content_index, perch2_content_items, perch2_content_regions, perch2_content_resources, perch2_forms, perch2_forms_responses, perch2_navigation, perch2_navigation_pages, perch2_page_templates, perch2_pages, perch2_resources, perch2_settings, perch2_user_privileges, perch2_user_role_privileges, perch2_user_roles, perch2_users
Users: 2
App runtimes:
<?php
    include(PERCH_PATH.'/core/apps/content/runtime.php');
    include(PERCH_PATH.'/addons/apps/perch_forms/runtime.php');
?>
Editor plug-ins: markitup
H1: e92db0d6eb3043f3267533039a602786
L1: 1b2582ebd3d9695010bf0055232dd9e1
headerColour: #ffffff
content_singlePageEdit: 1
helpURL:
siteURL: /
hideBranding: 1
content_collapseList: 0
lang: en-gb
update_2.4.9: done
latest_version: 2.5.3
on_sale_version: 2.6
headerScheme: light
dashboard: 0
hide_pwd_reset: 0
content_hideNonEditableRegions: 0
content_frontend_edit: 0
logoPath: /perch/resources/fransons-logo.png
perch_backup_mysqldump_path: /usr/bin/mysqldump
PERCH_DEVELOPMENT: 10
PERCH_STAGING: 50
PERCH_PRODUCTION: 100
PERCH_DB_USERNAME: fransons_user
PERCH_DB_SERVER: localhost
PERCH_DB_DATABASE: fransons_perch
PERCH_PRODUCTION_MODE: 100
PERCH_DB_PREFIX: perch2_
PERCH_TZ: Europe/Paris
PERCH_EMAIL_FROM: gary@fransons.fr
PERCH_EMAIL_FROM_NAME: Fransons
PERCH_LOGINPATH: /perch
PERCH_PATH: /home/fransons/public_html/perch
PERCH_CORE: /home/fransons/public_html/perch/core
PERCH_RESFILEPATH: /home/fransons/public_html/perch/resources
PERCH_RESPATH: /perch/resources
PERCH_HTML5: 1
PERCH_ERROR_MODE: DIE
PERCH_DATE_LONG: %d %B %Y
PERCH_DATE_SHORT: %d %b %Y
PERCH_TIME_SHORT: %H:%M
PERCH_TIME_LONG: %H:%M:%S
PERCH_DEBUG:
PERCH_PREVIEW_ARG: preview
PERCH_TEMPLATE_PATH: /home/fransons/public_html/perch/templates
PERCH_DEFAULT_DOC: index.php
PERCH_DEFAULT_EXT: .php
PERCH_RWD:
PERCH_HTML_ENTITIES:
PERCH_SSL:
PERCH_AUTH_PLUGIN:
PERCH_DB_CHARSET: utf8
PERCH_DB_PORT:
PERCH_DB_SOCKET:
HOSTING SETTINGS

PHP: 5.4.27
Zend: 2.4.0
OS: Linux
SAPI: cgi-fcgi
Safe mode: not detected
MySQL client: mysqlnd 5.0.10 - 20111026 - $Id: c85105d7c6f7d70d609bb4c000257868a40840ab $
MySQL server: 5.5.37-cll
Extensions: Core, date, ereg, libxml, openssl, pcre, sqlite3, zlib, bcmath, bz2, calendar, ctype, curl, dom, enchant, hash, fileinfo, filter, ftp, gd, gettext, SPL, iconv, session, intl, json, mbstring, mcrypt, standard, mysql, mysqli, mysqlnd, apc, pspell, Reflection, imap, SimpleXML, snmp, soap, sockets, exif, tidy, tokenizer, wddx, xml, xmlreader, xmlrpc, xmlwriter, xsl, zip, cgi-fcgi, PDO, pdo_sqlite, pdo_mysql, Phar, timezonedb, memcache, ionCube Loader, Zend Guard Loader
GD: Yes
ImageMagick: No
PHP max upload size: 256M
PHP max form post size: 256M
PHP memory limit: 256M
Total max uploadable file size: 256M
Resource folder writeable: Yes
Session timeout: 24 minutes
Native JSON: Yes
Filter functions: Yes
Transliteration functions: Yes
DOCUMENT_ROOT: /home/fransons/public_html
GATEWAY_INTERFACE: CGI/1.1
HTTP_ACCEPT: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
HTTP_ACCEPT_ENCODING: gzip,deflate,sdch
HTTP_ACCEPT_LANGUAGE: en-US,en;q=0.8,en-GB;q=0.6
HTTP_CONNECTION: keep-alive
HTTP_COOKIE: _ga=GA1.2.181502841.1407221805; cmsa=1; PHPSESSID=0281bd01b1f3e3a96aecf3f70577e1b8
HTTP_HOST: fransons.fr
HTTP_REFERER: https://fransons.fr/perch/core/settings/
HTTP_USER_AGENT: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/36.0.1985.143 Safari/537.36
PATH: /bin:/usr/bin
REDIRECT_STATUS: 200
REMOTE_ADDR: 2.125.230.14
REMOTE_PORT: 53339
REQUEST_METHOD: GET
REQUEST_URI: /perch/core/settings/diagnostics/
SCRIPT_FILENAME: /home/fransons/public_html/perch/core/settings/diagnostics/index.php
SCRIPT_NAME: /perch/core/settings/diagnostics/index.php
SERVER_ADDR: 143.95.98.244
SERVER_ADMIN: webmaster@fransons.fr
SERVER_NAME: fransons.fr
SERVER_PORT: 80
SERVER_PROTOCOL: HTTP/1.1
SERVER_SOFTWARE: Apache
UNIQUE_ID: U-WSSMZZfjsAAHi9bbgAAAAB
PHP_SELF: /perch/core/settings/diagnostics/index.php
REQUEST_TIME_FLOAT: 1408602696,86
REQUEST_TIME: 1408602696