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Description:

mailers 3.0.5

Mailers for asyncio

Features

fully typed
full utf-8 support
async and sync sending
pluggable transports
multiple built-in transports including: SMTP, file, null, in-memory, streaming, and console.
message preprocessors
embeddables
attachments (with async and sync interfaces)
message signing via Signer interface (DKIM bundled)
message encryption via Encrypter interface
trio support via anyio (the library itself, some backends may not be compatible)
fallback transports
global From address
templated emails

Usage
pip install mailers[smtp]

Then create mailer:
from mailers import Mailer

mailer = Mailer("smtp://user:password@localhost:25?timeout=2")
await mailer.send_message(
to="user@localhost", from_address="from@localhost", subject="Hello", text="World!"
)

Compose messages
If you need more control over the message, you can use Email object to construct email message and then send it
using mailer.send method.
from mailers import Email, Mailer

message = Email(
to="user@localhost",
from_address="from@example.tld",
cc="cc@example.com",
bcc=["bcc@example.com"],
text="Hello world!",
html="<b>Hello world!</b>",
)
mailer = Mailer("smtp://")
await mailer.send(message)

Global From address
Instead of setting "From" header in every message, you can set it mailer-wide. Use from_address argument of Mailer
class:
mailer = Mailer(from_address="sender@localhost")

The mailer will set From header with the given value to all messages that do not container From or Sender headers.
Using Jinja templates

Requires jinja2 package installed

You can use Jinja to render templates. This way, your text and html can be rendered from a template.
Use TemplatedMailer instead of default Mailer and set a jinja2.Environment instance.
Then, call send_templated_message.
import jinja2

from mailers import TemplatedMailer

env = jinja2.Environment(loader=jinja2.FileSystemLoader(["templates"]))
mailer = TemplatedMailer("smtp://", env)
mailer.send_templated_message(
to="...",
subject="Hello",
text_template="mail.txt",
html_template="mail.html",
template_context={"user": "root"},
)

Attachments
Use attach, attach_from_path, attach_from_path_sync methods to attach files.
from mailers import Email

message = Email(
to="user@localhost", from_address="from@example.tld", text="Hello world!"
)

# attachments can be added on demand
await message.attach_from_path("file.txt")

# or use blocking sync version
message.attach_from_path_sync("file.txt")

# attach from variable
message.attach("CONTENTS", "file.txt", "text/plain")

Embedding files
In the same way as with attachments, you can inline file into your messages. This is commonly used to display embedded
images in the HTML body. Here are method you can use embed, embed_from_path, embed_from_path_sync.
from mailers import Email

message = Email(
to="user@localhost",
from_address="from@example.tld",
html='Render me <img src="cid:img1">',
)

await message.embed_from_path(path="/path/to/image.png", name="img1")

Note, that you have to add HTML part to embed files. Otherwise, they will be ignored.
Message signatures
You can sign messages (e.g. with DKIM) by passing signer argument to the Mailer instance.
signer = MySigner()
mailer = Mailer(..., signer=signer)

DKIM signing

Requires dkimpy package installed

You may wish to add DKIM signature to your messages to prevent them from being put into the spam folder.
Note, you need to install dkimpy package before using this feature.
from mailers import Mailer
from mailers.signers.dkim import DKIMSigner

signer = DKIMSigner(selector="default", private_key_path="/path/to/key.pem")

# or you can put key content using private_key argument
signer = DKIMSigner(selector="default", private_key="PRIVATE KEY GOES here...")

mailer = Mailer("smtp://", signer=signer)

Now all outgoing messages will be signed with DKIM method.
The plugin signs "From", "To", "Subject" headers by default. Use "headers" argument to override it.
Custom signers
Extend mailers.Signer class and implement sign method:
from email.message import Message
from mailers import Signer

class MySigner(Signer):
def sign(self, message: Message) -> Message:
# message signing code here...
return message

Encrypters
When encrypting a message, the entire message (including attachments) is encrypted using a certificate. Therefore, only
the recipients that have the corresponding private key can read the original message contents.
encrypter = MyEncrypter()
mailer = Mailer(..., encrypter=encrypter)

Now all message content will be encrypted.
Custom encrypters
Extend mailers.Encrypter class and implement encrypt method:
from email.message import Message
from mailers import Encrypter

class MyEncrypter(Encrypter):
def encrypt(self, message: Message) -> Message:
# message encrypting code here...
return message

High Availability
Use MultiTransport to provide a fallback transport. By default, the first transport is used but if it fails to send
the message, it will retry sending using next configured transport.
from mailers import Mailer, MultiTransport, SMTPTransport

primary_transport = SMTPTransport()
fallback_transport = SMTPTransport()

mailer = Mailer(MultiTransport([primary_transport, fallback_transport]))

Preprocessors
Preprocessors are function that mailer calls before sending. Preprocessors are simple functions that modify message
contents.
Below you see an example preprocessor:
from email.message import EmailMessage

from mailers import Mailer

def attach_html_preprocessor(message: EmailMessage) -> EmailMessage:
message.add_alternative(b"This is HTML body", subtype="html", charset="utf-8")
return message

mailer = Mailer(preprocessors=[attach_html_preprocessor])

CSS inliner

Requires toronado package installed

Out of the box we provide mailers.preprocessors.css_inliner utility that converts CSS classes into inline styles.
Transports
SMTP transport

Requires aiosmtplib package installed

Send messages via third-party SMTP servers.
Class: mailers.transports.SMTPTransport
directory smtp://user:pass@hostname:port?timeout=&use_tls=1
Options:

host (string, default "localhost") - SMTP server host
port (string, default "25") - SMTP server port
user (string) - SMTP server login
password (string) - SMTP server login password
use_tls (string, choices: "yes", "1", "on", "true") - use TLS
timeout (int) - connection timeout
cert_file (string) - path to certificate file
key_file (string) - path to key file

File transport
Write outgoing messages into a directory in EML format.
Class: mailers.transports.FileTransport
DSN: file:///tmp/mails
Options:

directory (string) path to a directory

Null transport
Discards outgoing messages. Takes no action on send.
Class: mailers.transports.NullTransport
DSN: null://
Memory transport
Keeps all outgoing messages in memory. Good for testing.
Class: mailers.transports.InMemoryTransport
DSN: memory://
Options:

storage (list of strings) - outgoing message container

You can access the mailbox via ".mailbox" attribute.
Example:
from mailers import Mailer, InMemoryTransport, Email

transport = InMemoryTransport([])
mailer = Mailer(transport)

await mailer.send(Email(...))
assert len(transport.mailbox) == 1 # here are all outgoing messages

Streaming transport
Writes all messages into a writable stream. Ok for local development.
Class: mailers.transports.StreamTransport
DSN: unsupported
Options:

output (typing.IO) - a writable stream

Example:
import io
from mailers import Mailer, StreamTransport

transport = StreamTransport(output=io.StringIO())
mailer = Mailer(transport)

Console transport
This is a preconfigured subclass of streaming transport. Writes to sys.stderr by default.
Class: mailers.transports.ConsoleTransport
DSN: console://
Options:

output (typing.IO) - a writeable stream

Multi transport
The purpose of this transport is to provide a developer an option to provide a fallback transport.
You can configure several channels and MultiTransport will guarantee that at least one will deliver the message.
Class: mailers.transports.MultiTransport
DSN: -
Options:

transports (list[Transport]) - subtransports

Custom transports.
Each transport must extend mailers.transports.Transport base class.
from email.message import Message
from mailers import Mailer, Transport

class PrintTransport(Transport):
async def send(self, message: Message) -> None:
print(str(message))

mailer = Mailer(PrintTransport())