Awesome
Colombe - an implementation of SMTP protocol in OCaml
colombe
is a little library which wants to implement the SMTP protocol
according RFC5321. It is a low-level library used by some others projects to
implements clients or servers.
The library does not handle properly an email. If you want to generate a proper email or introspect an email, you should be interested by mrmime.
As a client
The distribution provides sendmail
, sendmail.starttls
and sendmail-lwt
which are respectively:
- An agnostic (to the system) implementation of an usual client with authentication
- An agnostic (to the system) implementation of an usual client with
authentication and
STARTTLS
extension - An LWT implementation of an usual client with authentication
Depending on your context:
- If you want to communicate with a SMTP server which require a TLS connection
(like,
*:465
),sendmail
with a scheduler such as LWT or ASYNC (or UNIX) should be use.sendmail-lwt
is a specialization with LWT. - If you want to communicate with a SMTP server which handles (and surely
requires)
STARTTLS
extension, (like*:587
),sendmail.starttls
with a scheduler should be use.
Of course, a client can be more complex and can handle:
- file attachments
- a well formed email
- some usual metadata such as the timezone
If you are interested by that, you should look into facteur which
wants to provide a little binary to send an email with a nice use between
colombe
, mrmime
and some others MirageOS projects.
As a server
Of course, colombe
implements both sides. By this library, you are able to
implement an SMTP server - if you are interested by that, you should look into
ptt.
How to use colombe
As we said, the library wants to be a low-level one. At least, the core does not handle properly eSMTP extensions or any high mechanisms such the authentication. It's mostly because the library wants to be used by a server implementation and a client implementation.
It only ensures a high abstracted interface on top of the low-level of the communication. The library defines only few parts of the SMTP protocol and a monadic interface to describe the state-machine while the communication with an other peer.
sendmail
is a good example about how to use colombe
. It describes
structurally the SMTP protocol (only what it really needs) and the state machine
to send an email.
Received field
RFC5321 describes the SMTP protocols and some mechanisms such as the Received:
field. The distribution provides a way to introspect Received:
fields (and can
produce a graph of them) or generate them from a server configuration.
Credits
colombe
has received funding from the Next Generation Internet Initiative (NGI)
within the framework of the DAPSI Project.