diff --git a/app/models.py b/app/models.py
index 50e4b029..819b134b 100644
--- a/app/models.py
+++ b/app/models.py
@@ -1622,6 +1622,11 @@ class EmailLog(Base, ModelMixin):
         sa.ForeignKey("mailbox.id", ondelete="cascade"), nullable=True
     )
 
+    # the Message ID
+    message_id = deferred(sa.Column(sa.String(512), nullable=True))
+    # in the reply phase, the original message_id is replaced by the SL message_id
+    sl_message_id = deferred(sa.Column(sa.String(512), nullable=True))
+
     refused_email = orm.relationship("RefusedEmail")
     forward = orm.relationship(Contact)
 
@@ -2566,3 +2571,13 @@ class IgnoreBounceSender(Base, ModelMixin):
 
     def __repr__(self):
         return f"<NoReplySender {self.mail_from}"
+
+
+class MessageIDMatching(Base, ModelMixin):
+    """Store the SL Message ID and the original Message ID"""
+
+    __tablename__ = "message_id_matching"
+
+    # SimpleLogin Message ID
+    sl_message_id = sa.Column(sa.String(512), unique=True, nullable=False)
+    original_message_id = sa.Column(sa.String(512), unique=True, nullable=False)
diff --git a/migrations/versions/2021_101817_99d9e329b27f_.py b/migrations/versions/2021_101817_99d9e329b27f_.py
new file mode 100644
index 00000000..b2bd8ef1
--- /dev/null
+++ b/migrations/versions/2021_101817_99d9e329b27f_.py
@@ -0,0 +1,42 @@
+"""empty message
+
+Revision ID: 99d9e329b27f
+Revises: 2f1b3c759773
+Create Date: 2021-10-18 17:15:29.903802
+
+"""
+import sqlalchemy_utils
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '99d9e329b27f'
+down_revision = '2f1b3c759773'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.create_table('message_id_matching',
+    sa.Column('id', sa.Integer(), autoincrement=True, nullable=False),
+    sa.Column('created_at', sqlalchemy_utils.types.arrow.ArrowType(), nullable=False),
+    sa.Column('updated_at', sqlalchemy_utils.types.arrow.ArrowType(), nullable=True),
+    sa.Column('sl_message_id', sa.String(length=512), nullable=False),
+    sa.Column('original_message_id', sa.String(length=512), nullable=False),
+    sa.PrimaryKeyConstraint('id'),
+    sa.UniqueConstraint('original_message_id'),
+    sa.UniqueConstraint('sl_message_id')
+    )
+    op.add_column('email_log', sa.Column('message_id', sa.String(length=512), nullable=True))
+    op.add_column('email_log', sa.Column('sl_message_id', sa.String(length=512), nullable=True))
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_column('email_log', 'sl_message_id')
+    op.drop_column('email_log', 'message_id')
+    op.drop_table('message_id_matching')
+    # ### end Alembic commands ###