diff --git a/addons/snailmail/i18n/snailmail.pot b/addons/snailmail/i18n/snailmail.pot
index 5c1f4f4ed77..abe2e48530c 100644
--- a/addons/snailmail/i18n/snailmail.pot
+++ b/addons/snailmail/i18n/snailmail.pot
@@ -4,10 +4,10 @@
 #
 msgid ""
 msgstr ""
-"Project-Id-Version: Odoo Server saas~11.5\n"
+"Project-Id-Version: Odoo Server 12.0\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2018-10-02 10:06+0000\n"
-"PO-Revision-Date: 2018-10-02 10:06+0000\n"
+"POT-Creation-Date: 2018-10-30 12:25+0000\n"
+"PO-Revision-Date: 2018-10-30 12:25+0000\n"
 "Last-Translator: <>\n"
 "Language-Team: \n"
 "MIME-Version: 1.0\n"
@@ -16,13 +16,13 @@ msgstr ""
 "Plural-Forms: \n"
 
 #. module: snailmail
-#: code:addons/snailmail/models/snailmail_letter.py:243
+#: code:addons/snailmail/models/snailmail_letter.py:249
 #, python-format
 msgid "An error occured when sending the document by post.<br>Error: %s"
 msgstr ""
 
 #. module: snailmail
-#: code:addons/snailmail/models/snailmail_letter.py:211
+#: code:addons/snailmail/models/snailmail_letter.py:215
 #, python-format
 msgid "An unknown error happened. Please contact the support."
 msgstr ""
@@ -161,7 +161,7 @@ msgid "Model"
 msgstr ""
 
 #. module: snailmail
-#: code:addons/snailmail/models/snailmail_letter.py:209
+#: code:addons/snailmail/models/snailmail_letter.py:211
 #, python-format
 msgid "One or more required fields are empty."
 msgstr ""
@@ -172,7 +172,7 @@ msgid "Optional report to print and attach"
 msgstr ""
 
 #. module: snailmail
-#: code:addons/snailmail/models/snailmail_letter.py:248
+#: code:addons/snailmail/models/snailmail_letter.py:264
 #, python-format
 msgid "Post letter: an error occured."
 msgstr ""
@@ -235,13 +235,19 @@ msgid "Status"
 msgstr ""
 
 #. module: snailmail
-#: code:addons/snailmail/models/snailmail_letter.py:207
+#: code:addons/snailmail/models/snailmail_letter.py:213
+#, python-format
+msgid "The attachment of the letter could not be sent. Please check its content and contact the support if the problem persists."
+msgstr ""
+
+#. module: snailmail
+#: code:addons/snailmail/models/snailmail_letter.py:209
 #, python-format
 msgid "The country of the partner is not covered by Snailmail."
 msgstr ""
 
 #. module: snailmail
-#: code:addons/snailmail/models/snailmail_letter.py:238
+#: code:addons/snailmail/models/snailmail_letter.py:242
 #, python-format
 msgid "The document was correctly sent by post.<br>The tracking id is %ssend_id"
 msgstr ""
@@ -259,14 +265,13 @@ msgid "When a letter is created, the status is 'Draft'.\n"
 msgstr ""
 
 #. module: snailmail
-#: code:addons/snailmail/models/snailmail_letter.py:205
+#: code:addons/snailmail/models/snailmail_letter.py:207
 #, python-format
 msgid "You don't have an IAP account registered for this service.<br>Please go to <a href=%s target=\"new\">iap.odoo.com</a> to claim your free credits."
 msgstr ""
 
 #. module: snailmail
-#: code:addons/snailmail/models/snailmail_letter.py:202
+#: code:addons/snailmail/models/snailmail_letter.py:204
 #, python-format
 msgid "You don't have enough credits to perform this operation.<br>Please go to your <a href=%s target=\"new\">iap account</a>."
 msgstr ""
-
diff --git a/addons/snailmail/models/snailmail_letter.py b/addons/snailmail/models/snailmail_letter.py
index 7024edfec34..b21d6aacb60 100644
--- a/addons/snailmail/models/snailmail_letter.py
+++ b/addons/snailmail/models/snailmail_letter.py
@@ -209,7 +209,9 @@ class SnailmailLetter(models.Model):
             return _('The country of the partner is not covered by Snailmail.')
         if error == 'MISSING_REQUIRED_FIELDS':
             return _('One or more required fields are empty.')
-        if error == 'SOMETHING_IS_WRONG':
+        if error == 'FORMAT_ERROR':
+            return _('The attachment of the letter could not be sent. Please check its content and contact the support if the problem persists.')
+        else:
             return _('An unknown error happened. Please contact the support.')
         return error