Add a footer to outgoing messages that point to where sender keys can be feched. Closes #4526.
Add a header that reflects the validity of incoming signatures. Closes #4354.
Add the preference parameter to openpgp header. Closes #3878.
Fix smtp tests to accept deferred and new param encoding.
Merge remote-tracking branch 'drebs/feature/4526_4354_header-and-footer' into develop
Fail gracefully when failing to decrypt incoming messages. Closes #4589.
Merge remote-tracking branch 'drebs/bug/4589_fail-gracefully-when-failing-to-decrypt-incoming-messages' into develop
reduce polling time to one minute
Merge remote-tracking branch 'kali/feature/reduce_polling_time' into develop
Fix fetch iteration on empty folder
fix adding msg with empty flags
Merge remote-tracking branch 'refs/remotes/kali/bug/mailbox-fixes' into develop
add message producer and consumer
use messageproducer to write messages to soledad
add changes file
Merge remote-tracking branch 'refs/remotes/kali/feature/message-flow' into develop
add with_venvwrapper script
Merge remote-tracking branch 'refs/remotes/kali/feature/virtualenvwrapper-tests' into develop
Update requirements
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