zope.sendmail

zope.sendmail is a package for email sending from Zope 3 applications. Email sending from Zope 3 applications works as follows:

A Zope 3 application locates a mail delivery utility (IMailDelivery) and feeds a message to it. It gets back a unique message ID so it can keep track of the message by subscribing to IMailEvent events.

The utility registers with the transaction system to make sure the message is only sent when the transaction commits successfully. (Among other things this avoids duplicate messages on ConflictErrors.)

If the delivery utility is a IQueuedMailDelivery, it puts the message into a queue (a Maildir mailbox in the file system). A separate process or thread (IMailQueueProcessor) watches the queue and delivers messages asynchronously. Since the queue is located in the file system, it survives Zope restarts or crashes and the mail is not lost. The queue processor can implement batching to keep the server load low.

If the delivery utility is a IDirectMailDelivery, it delivers messages synchronously during the transaction commit. This is not a very good idea, as it makes the user wait. Note that transaction commits must not fail, but that is not a problem, because mail delivery problems dispatch an event instead of raising an exception.

However, there is a problem -- sending events causes unknown code to be executed during the transaction commit phase. There should be a way to start a new transaction for event processing after this one is commited.

An IMailQueueProcessor or IDirectMailDelivery actually delivers the messages by using a mailer (IMailer) component that encapsulates the delivery process. There currently is only one mailer:

ISMTPMailer sends all messages to a relay host using SMTP.

Documentation is hosted at

Changes

6.2 (2024-03-21)

• Add implicit_tls option to the Mailer, if setted to True the SMTP connection will use smtplib.SMTP_SSL and starts the connection with SSL from the beginning. (see RFC8314)

6.1 (2024-02-07)

• Fix SMTP protocol interoperability by avoiding hardcoded line endings. (see )
• Add preliminary support for Python 3.13 as of 3.13a3.
• Add support for Python 3.12.

6.0 (2023-08-22)

• Drop support for Python 2.7, 3.5, 3.6.
• Add support for Python 3.11.

5.3 (2022-10-06)

• Add support for Python 3.10.
• Do not try to send queued emails to an empty address (#45).

5.2 (2021-01-18)

• Add minimal savepoint support, so we do not fail if any code tries to create a savepoint. (#35).
• Fix TypeError: 'error' object is not subscriptable during error handling on Windows (#33).
• Add support for Python 3.9.

5.1 (2020-07-31)

• Use pywin32 again, not any longer the meanwhile outdated fork named pypiwin32. Add some information for installation with buildout. (#30)
• Support bytes messages; consistently convert messages using a "text" type (i.e. str for Python 3, unicode for Python 2) into bytes via utf-8 encoding. Prerequisite to fix Products.MailHost#30.

5.0 (2019-04-03)

• Drop support for Python 3.4.
• Add support for Python 3.8a3.
• Fix text/bytes issue in MailDir for Python 3. (#24)

4.2.1 (2019-02-07)

• Fix SMTP authentication on Python 3. See issue 16.

4.2 (2018-10-10)

• Add support for Python 3.7.

4.1.0 (2017-09-02)

• Host documentation at
• Make the data manager sort key a string, this fixes Python 3 where strings and integers are not sortable. This would happen when using other data managers with string sort keys.
• Add support for Python 3.5 and 3.6.
• Drop support for Python 2.6 and 3.3.
• Declare explicit dependency on pywin32 on Windows.
• Replace hard-coded constants with equivalents from the standard errno module.
• Fix SSL support on Python 3. See issue 9.
• Reach 100% test coverage and maintain it via tox.ini and Travis CI.
• Replaced deprecated dependency on optparse with equivalent argparse. The help messages have changed and errors are generally more clear. Specifying a --config path that doesn't exist is now an error instead of being silently ignored.
• Fix SMTPMailer sending more than one message. It now reconnects to the SMTP server as needed. Previously it could only send one message since it closed the connection after each send. This also makes the SMTPMailer thread safe. See issue 1.

4.0.1 (2014-12-29)

• Add support for PyPy3.

4.0.0 (2014-12-20)

• Add support for testing on Travis-CI against supported Python verisons.
• Drop use of zope.testrunner for testing.
• Drop dependency on six.
• Replace doctests with equivalent unittests.

4.0.0a2 (2013-02-26)

• Fix license Trove classifier.

4.0.0a1 (2013-02-25)

• Add support for Python 3.3.

• Delete event fossils (interfaces zope.sendmail.interfaces.IMailSent and zope.sendmail.interfaces.IMailError. plus the zope.sendmail.events module and associated tests). These events were never emitted, and couldn't have been used safely even if they had been, due to two-phase commit.

• Replace deprecated zope.interface.classProvides usage with equivalent zope.interface.provider decorator.

• Replace deprecated zope.interface.implements usage with equivalent zope.interface.implementer decorator.

• Drop support for Python 2.4 and 2.5.

• Add a vote method to Mailer implementations to allow them to abort a transaction if it is known to be unsafe.

• Prevent fatal errors in mail delivery causing potential database corruption.

• Add not declared, but needed test dependency on zope.component [test].

• Add handling for unicode usernames and passwords, encoding them to UTF-8. Fix for

• Give the background queue processor thread a name.

• Document the ini file keys for zope-sendmail --config in the help message printed by zope-sendmail --help. Also rewrote the command-line parsing to use optparse (not argparse, since Python 2.6 is still supported).

3.7.5 (2012-05-23)

• Ensure that the 'queuedDelivery' directive has the same discriminator as the 'directDelivery' directive (they are mutually incompatible).

• Avoid requeuing messages after an SMTP "recipients refused" error.

3.7.4 (2010-10-01)

• Handle unicode usernames and passwords, encoding them to UTF-8. Fix for

3.7.3 (2010-09-25)

• Add not declared, but needed test dependency on zope.component [test].

3.7.2 (2010-04-30)

• Remove no longer required testing dependency on zope.testing.
• Maildir storage for queue can now handle unicode passed in for message or to/from addresses (change backported from repoze.sendmail).
• Tests use stdlib doctest instead of zope.testing.doctest.

3.7.1 (2010-01-13)

• Backward compatibility import of zope.sendmail.queue.QueueProcessorThread in zope.sendmail.delivery.

3.7.0 (2010-01-12)

• Remove dependency on zope.security: the security support is optional, and only available if the zope.security package is available. This change is similar to the optional security support introduced in zope.component 3.8.0, and in fact it uses the same helpers.
• Sort by modification time the messages in zope.sendmail.maildir so earlier messages are sent before later messages during queue processing.
• Add the new parameter processorThread to the queuedDelivery ZCML directive: if False, the QueueProcessorThread is not started and thus an independent process must process the queue; it defaults to True for b/c.
• Provide a console script zope-sendmail which can be used to process the delivery queue in case processorThread is False. The console script can either process the messages in the queue once, or run in "daemon" mode.

3.6.1 (2009-11-16)

• Depend on zope.component >= 3.8.0, which supports the new semantic of zope.component.zcml.proxify needed by zope.sendmail.zcml.

3.6.0 (2009-09-14)

• Use simple vocabulary factory function instead of custom UtilityTerm and UtilityVocabulary classes, copied from zope.app.component in the previous release.
• Depend on the transaction package instead of ZODB3.
• Remove zcml slugs and zpkg-related files.
• Work around problem when used with Python >=2.5.1. See .

3.5.1 (2009-01-26)

• Copyover the UtilityTerm and UtilityVocabulary implementation from zope.app.component to avoid a dependency.
• Work around a problem when smtp quit fails, the mail was considered not delivered where just the quit failed.

3.5.0 (2008-07-05)

• final release (identical with 3.5.0b2)

3.5.0b2 (2007-12-19)

• If the SMTP server rejects a message (for example, when the sender or recipient address is malformed), that email stays in the queue forever ().

3.5.0b1 (2007-11-08)

• Add README.txt
• Can now talk to servers that don't implement EHLO
• Fix bug that caused files with very long names to be created
• Fix for : move aside mail that's causing 5xx server responses.

3.5.0a2 (2007-10-23)

• Clean up does_esmtp in faux SMTP connection classes provided by the tests.
• If the QueueProcessorThread is asked to stop while sending messages, do so after sending the current message; previously if there were many, many messages to send, the thread could stick around for quite a while.

3.5.0a1 (2007-10-23)

• QueueProcessorThread now accepts an optional parameter interval for defining how often to process the mail queue (default is 3 seconds)
• Several QueueProcessorThreads (either in the same process, or multiple processes) can now deliver messages from a single maildir without duplicates being sent.

3.4.0 (2007-08-20)

• Bugfix: Don't keep open files around for every email message to be sent on transaction commit. People who try to send many emails in a single transaction now will not run out of file descriptors.

3.4.0a1 (2007-04-22)

Initial release as a separate project, corresponds to zope.sendmail from Zope 3.4.0a1.