possible error in email input

app.py

@@ -61,10 +61,11 @@ with st.sidebar:
     # prevent user from clicking 'Find domains' button if email or sequence is empty
     domains_submitted = False
     if st.button('Find domains'):
-        if 'email' in st.session_state and 'sequence' in st.session_state:
+        if 'email' in st.session_state and 'sequence' in st.session_state and '@' in st.session_state.email:
             domains_submitted = True
+            st.session_state.disabled = True
         else:
-            st.warning('Please enter your email and protein sequence first.')
+            st.warning('Please enter your email and protein sequence first. If you have already entered your email and protein sequence, please check that your email is valid.')
     else:
         with domain_tab:
             st.warning('Please enter your query and click "Find domains" to see domains in sequence.')