fix: make bulk_email send email task handles a retryable exception

[ghassanmas]

Description

According to bulk_email and SMTP doc, when an error code is between
(400-499) it can be retried after sometime, this commit adds a new
type of exception called SMTPSenderRefused, so it can be retried
if it's code fails under above constraint.

Useful information to include:

• Which edX user roles will this change impact? Common user roles are "Learner", "Course Author",
  "Developer", and "Operator".
• Include screenshots for changes to the UI (ideally, both "before" and "after" screenshots, if applicable).
• Provide links to the description of corresponding configuration changes. Remember to correctly annotate these
  changes.

Supporting information

The issue have been reported at the forums

Testing instructions

Please provide detailed step-by-step instructions for testing this change.

Deadline

"None" if there's no rush, or provide a specific date or event (and reason) if there is one.

Other information

Include anything else that will help reviewers and consumers understand the change.

• Does this change depend on other changes elsewhere?
• Any special concerns or limitations? For example: deprecations, migrations, security, or accessibility.

[openedx-webhooks]

Thanks for the pull request, @ghassanmas! I've created OSPR-6157 to keep track of it in JIRA, where we prioritize reviews. Please note that it may take us up to several weeks or months to complete a review and merge your PR.

Feel free to add as much of the following information to the ticket as you can:

• supporting documentation
• Open edX discussion forum threads
• timeline information ("this must be merged by XX date", and why that is)
• partner information ("this is a course on edx.org")
• any other information that can help Product understand the context for the PR

All technical communication about the code itself will be done via the GitHub pull request interface. As a reminder, our process documentation is here.

Please let us know once your PR is ready for our review and all tests are green.

[ghassanmas]

This PR is ready to be reviwed.

[natabene]

@ghassanmas Thank you for your contribution. Please let me know once this is ready for our review.

[edx-status-bot]

Your PR has finished running tests. There were no failures.

[ghassanmas]

@natabene It's ready now that all tests have passed

[ghassanmas]

@natabene any chance I might a look for this soon?
So far I have fixed two merge conflicts, and the issue has been reported again in the fourms

[natabene]

@ghassanmas Let me see what I can do.

[hurtstotouchfire]

Thanks @ghassanmas we will take a look at this. Sorry for the delay, it has been a pretty eventful couple quarters for us.

[justinhynes]

Hey @ghassanmas, thanks for your contribution!

I would love to see a test for the new logic added before accepting this change.

The bulk email tasks tests can be found here: /lms/djangoapps/bulk_email/tests/test_tasks.py. The relevant test class/suite would be TestBulkEmailInstructorTask.

[justinhynes]

Looks good to me. Thanks for adding the test (and for your patience!).

[ghassanmas]

It's alright no worries. It was just when a conflict occurs at that point I would have already forgotten what I actually did! Anyway thanks for your review

[natabene]

@ghassanmas We are looking into this and will get back to you soon

[hurtstotouchfire]

Tentatively hope to merge this in the morning.

[openedx-webhooks]

@ghassanmas 🎉 Your pull request was merged! Please take a moment to answer a two question survey so we can improve your experience in the future.

[edx-pipeline-bot]

EdX Release Notice: This PR has been deployed to the staging environment in preparation for a release to production.

[edx-pipeline-bot]

EdX Release Notice: This PR has been deployed to the production environment.

[edx-pipeline-bot]

EdX Release Notice: This PR has been deployed to the production environment.