Reject email addresses that known to be undeliverable during signup.
Some users signup with invalid email addresses, which causes the welcome
email (which contains the email confirmation link) to bounce. Too many
bounces hurt our ability to send mail.
We check that an email address is undeliverable by checking if the
domain has a mail server and if the server returns an invalid address
error when attempting to send mail. This isn't foolproof since some
servers don't return an error if the address doesn't exist. If the
checks fail we know the address is bad, but if the checks pass that
doesn't guarantee the address is good. However, this is still good
enough to filter out bad addresses for popular providers like Gmail and
Microsoft that do return nonexistent address errors.
The address existence check requires being able to connect to mail
servers over port 25. This may fail if your network blocks port 25,
which many home ISPs and hosting providers do by default.
* Make the bans, ip bans, ip addresses, and user feedbacks pages all
link to one another in the secondary links.
* Add quick search bars to the secondary links on these pages.
* Move old post archive tests to post version tests.
* Fix pool tests that assumed that multiple edits by the same user
weren't merged.
* Fix references to `is_active` and `notes` on artist model.
* Fix the pool version SQS service to always be mocked before every
test. Before we had to manually set it up before every test dealing
with pool versions.
* Fix it so that we reconnect to the post/pool version databases before
every test. Before using $ARCHIVE_DATABASE_URL to set the database url
failed because environment variables weren't loaded by dotenv yet when
connections were first established.
Side effects:
* The data-current-user-is-voter <body> attribute has been removed.
* {{upvote:self}} no longer works. {{upvote:<name>}} should be used instead.
