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..2b57ff70a5a 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
 
@@ -256,20 +258,22 @@ class SnailmailLetter(models.Model):
                 activity = MailActivity.search(domain, limit=1)
 
                 activity_data = {
-                    'res_id': letter.res_id,
-                    'res_model_id': self.env['ir.model']._get(letter.model).id,
                     'activity_type_id': self.env.ref('mail.mail_activity_data_warning').id,
                     'summary': '[SNAILMAIL] ' + _('Post letter: an error occured.'),
                     'note': note,
-                    'user_id': letter.user_id.id,
                     'date_deadline': fields.Date.today()
                 }
                 if activity:
                     activity.update(activity_data)
                 else:
+                    activity_data.update({
+                        'user_id': letter.user_id.id,
+                        'res_id': letter.res_id,
+                        'res_model_id': self.env['ir.model']._get(letter.model).id,
+                    })
                     MailActivity.create(activity_data)
 
-                letter.write({'info_msg': note})
+                letter.write({'info_msg': note, 'state': 'error'})
 
         self.env.cr.commit()
 
diff --git a/addons/snailmail_account/i18n/snailmail_account.pot b/addons/snailmail_account/i18n/snailmail_account.pot
index 94b580df10e..5f808e44312 100644
--- a/addons/snailmail_account/i18n/snailmail_account.pot
+++ b/addons/snailmail_account/i18n/snailmail_account.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: 2018-09-21 13:17+0000\n"
-"PO-Revision-Date: 2018-09-21 13:17+0000\n"
+"POT-Creation-Date: 2018-11-05 09:29+0000\n"
+"PO-Revision-Date: 2018-11-05 09:29+0000\n"
 "Last-Translator: <>\n"
 "Language-Team: \n"
 "MIME-Version: 1.0\n"
@@ -40,11 +40,6 @@ msgstr ""
 msgid "Config Settings"
 msgstr ""
 
-#. module: snailmail_account
-#: model:ir.model.fields,field_description:snailmail_account.field_account_invoice_send__snailmail_cost
-msgid "Credits"
-msgstr ""
-
 #. module: snailmail_account
 #: model:ir.model.fields,field_description:snailmail_account.field_account_invoice_send__currency_id
 msgid "Currency"
@@ -81,3 +76,7 @@ msgstr ""
 msgid "Send by Post"
 msgstr ""
 
+#. module: snailmail_account
+#: model:ir.model.fields,field_description:snailmail_account.field_account_invoice_send__snailmail_cost
+msgid "Stamp(s)"
+msgstr ""
diff --git a/addons/snailmail_account/wizard/account_invoice_send.py b/addons/snailmail_account/wizard/account_invoice_send.py
index 4aa2ee0adaf..75ca9c3cb85 100644
--- a/addons/snailmail_account/wizard/account_invoice_send.py
+++ b/addons/snailmail_account/wizard/account_invoice_send.py
@@ -11,17 +11,10 @@ class AccountInvoiceSend(models.TransientModel):
 
     partner_id = fields.Many2one('res.partner', compute='_get_partner', string='Partner')
     snailmail_is_letter = fields.Boolean('Send by Post', help='Allows to send the document by snail mail (coventional posting delivery service)', default=lambda self: self.env.user.company_id.invoice_is_snailmail)
-    snailmail_cost = fields.Float(string='Credits', compute='_snailmail_estimate', store=True, readonly=True)
+    snailmail_cost = fields.Float(string='Stamp(s)', compute='_snailmail_estimate', store=True, readonly=True)
     currency_id = fields.Many2one('res.currency', compute='_get_invoice_currency', string="Currency")
     letter_ids = fields.Many2many('snailmail.letter', 'snailmail_letter_account_invoice_send_rel', ondelete='cascade')
 
-    @api.multi
-    @api.onchange('invoice_ids')
-    def _get_invoice_currency(self):
-        for wizard in self:
-            if wizard.invoice_ids:
-                wizard.currency_id = wizard.invoice_ids.mapped('currency_id')[0].id
-
     @api.multi
     @api.onchange('invoice_ids')
     def _get_partner(self):
diff --git a/addons/snailmail_account/wizard/account_invoice_send_views.xml b/addons/snailmail_account/wizard/account_invoice_send_views.xml
index 134236397d6..5fd58f436e6 100644
--- a/addons/snailmail_account/wizard/account_invoice_send_views.xml
+++ b/addons/snailmail_account/wizard/account_invoice_send_views.xml
@@ -9,14 +9,16 @@
                 <xpath expr="//div[@name='option_email']" position='before'>
                     <div name="option_letter">
                         <field name="letter_ids" invisible="1"/>
-                        <field name="currency_id" invisible="1"/>
                         <div name="option" class="text-left d-inline-block">
                             <field name="snailmail_is_letter" />
                             <b><label for="snailmail_is_letter"/></b>
                         </div>
                         <div class="text-left d-inline-block mr8" name='cost' attrs="{'invisible': [('snailmail_is_letter','=', False)]}">
                             <b>(
-                                <field name="snailmail_cost" class="mr4" widget='monetary' options="{'currency_field': 'currency_id'}"/>
+                                <span>
+                                    <field name="snailmail_cost" options="{'digits':[0,0]}" class="mr4"/>
+                                    <label for="snailmail_cost" class="mr4"/>
+                                </span>
                                 <i class="fa fa-info-circle" role="img" aria-label="Warning" title="
                                 The letter will be sent using the IAP service from Odoo.&#10;Make sure you have enough credits on your account or proceed to a recharge.&#10;The price is estimated based on 1 page per document.
                                 "/>