Sending emails from streamlit app works locally but not when deployed

[Eli_Lowry]

Hi!

I’m working on an app in which I need to send emails at intervals. I’m using python’s smtplib. When I host the app locally, I have no issues, but when it’s deployed, I run into mysterious problems: Everything seems to go smoothly - the logs say the email has sent, no exceptions, I’ve even set smtplib’s log level to debug and can see that the entire SMTP client-server communication seems to be successful - but the emails never arrive. I think I’ve controlled for all other differences: same sender/receiver, same data being sent, etc. The only difference is where it’s hosted. Here’s an example of a minimal email app that causes me issues: https://minimal.streamlit.app/. Run locally, I receive the emails; hosted, I do not - identical in the logs. Any ideas? This may not properly be a streamlit-responsible issue, but I wondered if anyone else has had a similar problem when using streamlit.

Thank you!
Eli

[dataprofessor]

Hi @Eli_Lowry

There’s similar post on the use of smtplib for sending emails from a Streamlit app along with a solution that has a code snippet by my colleague @tonykip that you can use:

Send email with SMTP and Gmail address

Hello ! Thanks for your quick answer Unfortunately it doesn’t work. I’ve tried just about everything I can find on the forums. The python packages are well installed elsewhere. And I don’t have two-factor authentication enabled. I also followed the recommendations of Google

Hope this helps!

[Eli_Lowry]

Thank you! I had seen this post, and I don’t believe it’s relevant to the particular issue I’m having. The emails send just fine from a local instance (just not from the deployment on streamlit cloud) and this is a private mail server which doesn’t have any multifactor authentication or any such thing. All passwords etc. are set up the same locally and in the deployment. I was wondering if perhaps streamlit cloud is being blocked in some way from sending requests to send emails (although, like I said, the smtplib logs don’t suggest that). Is streamlit ever blacklisted in any way that you know of?

[Eli_Lowry]

@dataprofessor Any thoughts or similar issues?

[dataprofessor]

Hi,

This article seems to help in a relevant post

Sending Emails With Python – Real Python

Here’s the relevant post

How to create a pdf file and share through mail

Thanks a lot for the article!! After read i only do few correction of my code and work!!

Hope this helps

[tonykip]

Are you getting an error message from your exception in the code?

[Eli_Lowry]

Thank you! I tried using yagmail and ran into the very same issue.

[Eli_Lowry]

No, no exceptions are thrown and the SMTP debug logs don’t show anything problematic either.

[Eli_Lowry]

It seems to me that it has to do with our private mail server. My guess is that it is somehow flagging streamlit-hosted apps as insecure. I’m not sure why no errors are thrown, but seeing as how it works when deployed locally and I’ve exhausted implementation options, I think I’ll just have to either host a new mail server that I have more fine-grained control over or host my streamlit app elsewhere.

Thank you!

[tonykip]

Thank you for providing the details of your implementation. Please let us know if you find a better solution to this as am sure somebody will ask this in future.

[tonykip]

Mmh interesting. Might be the mail server issue as you mentioned in your recent reply.