mailyak

README

An elegant MIME mail library with support for attachments

A simple, easy to use email library for Go (golang).

• Full attachment support (attach anything that implements io.Reader)
• Send to multiple addresses at the same time, including BCC addresses.
• Supports composing multi-part messages (HTML and plain text emails for older clients)
• Write templates directly to the email body (implements io.Writer for convenience)
• Production ready - several million emails sent in a production environment
• Comprehensive unit tests

Installation

go get -v github.com/domodwyer/mailyak

Usage

// Create a new email - specify the SMTP host and auth
mail := mailyak.New("mail.host.com:25", smtp.PlainAuth("", "user", "pass", "mail.host.com"))

mail.To("dom@itsallbroken.com")
mail.From("nigerianprince@justneedshelp.com")
mail.FromName("Prince Fournineteen")

mail.Subject("Business proposition")

// mail.HTML() and mail.Plain() implement io.Writer, so you can do handy things like
// parse a template directly into the email body
if err := t.ExecuteTemplate(mail.HTML(), "htmlEmail", data); err != nil {
	panic(" 💣 ")
}

// Or set the body using a string setter
mail.Plain().Set("Get a real email client")

// And you're done! 
if err := mail.Send(); err != nil {
	panic(" 💣 ")
}

To send an attachment:

mail := mailyak.New("mail.host.com:25", smtp.PlainAuth("", "user", "pass", "mail.host.com"))

mail.To("dom@itsallbroken.com")
mail.From("oops@itsallbroken.com")
mail.Subject("I am a teapot")
mail.HTML().Set("Don't panic")

// input can be a bytes.Buffer, os.File, os.Stdin, etc.
// call multiple times to attach multiple files
mail.Attach("filename.txt", &input)

if err := mail.Send(); err != nil {
	panic(" 💣 ")
}

Notes

• Why "MailYak"? Because "MailyMcMailFace" is annoyingly long to type.
• You can use a single instance of mailyak to send multiple emails after changing the to/body/whatever fields, avoiding unnecessary allocation/GC pressure.
• Attachments are read when you call Send() to prevent holding onto multiple copies of the attachment in memory (source and email) - this means changing the attachment data between calling Attach() and Send() will change what's emailed out!
• For your own sanity you should vendor this, and any other libraries when going into production, I recommend govendor.

Documentation

Overview

Package mailyak provides a simple interface for generating MIME compliant emails, and optionally sending them over SMTP.

Both plain-text and HTML email body content is supported, and their types implement io.Writer allowing easy composition directly from templating engines, etc.

Attachments are fully supported (attach anything that implements io.Reader).

The raw MIME content can be retrieved using MimeBuf(), typically used with an API service such as Amazon SES that does not require using an SMTP interface.

Example

// Create a new email - specify the SMTP host and auth
mail := New("mail.host.com:25", smtp.PlainAuth("", "user", "pass", "mail.host.com"))

mail.To("dom@itsallbroken.com")
mail.From("nigerianprince@justneedshelp.com")
mail.FromName("Prince Anybody")

mail.Subject("Business proposition")

// Add a custom header
mail.AddHeader("X-TOTALLY-NOT-A-SCAM", "true")

// mail.HTMLWriter() and mail.PlainWriter() implement io.Writer, so you can
// do handy things like parse a template directly into the email body - here
// we just use io.WriteString()
if _, err := io.WriteString(mail.HTML(), "So long, and thanks for all the fish."); err != nil {
	panic(" :( ")
}

// Or set the body using a string helper
mail.Plain().Set("Get a real email client")

// And you're done!
if err := mail.Send(); err != nil {
	panic(" :( ")
}

Example (Attachments)

// This will be our attachment data
buf := &bytes.Buffer{}
io.WriteString(buf, "We're in the stickiest situation since Sticky the Stick Insect got stuck on a sticky bun.")

// Create a new email - specify the SMTP host and auth
mail := New("mail.host.com:25", smtp.PlainAuth("", "user", "pass", "mail.host.com"))

mail.To("dom@itsallbroken.com")
mail.From("nigerianprince@justneedshelp.com")
mail.HTML().Set("I am an email")

// buf could be anything that implements io.Reader
mail.Attach("sticky.txt", buf)

if err := mail.Send(); err != nil {
	panic(" :( ")
}

Index

• type BodyPart
  • func (w *BodyPart) Set(s string)
• type MailYak
  • func New(host string, auth smtp.Auth) *MailYak
  • func (m *MailYak) AddHeader(name, value string)
  • func (m *MailYak) Attach(name string, r io.Reader)
  • func (m *MailYak) AttachInline(name string, r io.Reader)
  • func (m *MailYak) AttachInlineWithMimeType(name string, r io.Reader, mimeType string)
  • func (m *MailYak) AttachWithMimeType(name string, r io.Reader, mimeType string)
  • func (m *MailYak) Bcc(addrs ...string)
  • func (m *MailYak) Cc(addrs ...string)
  • func (m *MailYak) ClearAttachments()
  • func (m *MailYak) From(addr string)
  • func (m *MailYak) FromName(name string)
  • func (m *MailYak) HTML() *BodyPart
  • func (m *MailYak) MimeBuf() (*bytes.Buffer, error)
  • func (m *MailYak) Plain() *BodyPart
  • func (m *MailYak) ReplyTo(addr string)
  • func (m *MailYak) Send() error
  • func (m *MailYak) String() string
  • func (m *MailYak) Subject(sub string)
  • func (m *MailYak) To(addrs ...string)
  • func (m *MailYak) WriteBccHeader(shouldWrite bool)

Examples

• Package
• Package (Attachments)
• BodyPart (String)
• BodyPart (Templates)

Types

type BodyPart

type BodyPart struct{ bytes.Buffer }

BodyPart is a buffer holding the contents of an email MIME part.

Example (String)

// Create a new email - specify the SMTP host and auth
mail := New("mail.host.com:25", smtp.PlainAuth("", "user", "pass", "mail.host.com"))

// Set the plain text email content using a string
mail.Plain().Set("Get a real email client")

Example (Templates)

// Create a new email
mail := New("mail.host.com:25", smtp.PlainAuth("", "user", "pass", "mail.host.com"))

// Our pretend template data
tmplData := struct {
	Language string
}{"Go"}

// Compile a template
tmpl, err := template.New("html").Parse("I am an email template in {{ .Language }}")
if err != nil {
	panic(" :( ")
}

// Execute the template directly into the email body
if err := tmpl.Execute(mail.HTML(), tmplData); err != nil {
	panic(" :( ")
}

func (*BodyPart) Set

func (w *BodyPart) Set(s string)

Set accepts a string s as the contents of a BodyPart, replacing any existing data.

type MailYak

type MailYak struct {
	// contains filtered or unexported fields
}

MailYak represents an email.

func New

func New(host string, auth smtp.Auth) *MailYak

New returns an instance of MailYak using host as the SMTP server, and authenticating with auth where required.

host must include the port number (i.e. "smtp.itsallbroken.com:25")

mail := mailyak.New("smtp.itsallbroken.com:25", smtp.PlainAuth(
	"",
	"username",
	"password",
	"stmp.itsallbroken.com",
))

func (*MailYak) AddHeader

func (m *MailYak) AddHeader(name, value string)

AddHeader adds an arbitrary email header.

If value contains non-ASCII characters, it is Q-encoded according to RFC1342. As always, validate any user input before adding it to a message, as this method may enable an attacker to override the standard headers and, for example, BCC themselves in a password reset email to a different user.

func (*MailYak) Attach

func (m *MailYak) Attach(name string, r io.Reader)

Attach adds the contents of r to the email as an attachment with name as the filename.

r is not read until Send is called and the MIME type will be detected using https://golang.org/pkg/net/http/#DetectContentType

func (*MailYak) AttachInline

func (m *MailYak) AttachInline(name string, r io.Reader)

AttachInline adds the contents of r to the email as an inline attachment. Inline attachments are typically used within the email body, such as a logo or header image. It is up to the user to ensure name is unique.

Files can be referenced by their name within the email using the cid URL protocol:

<img src="cid:myFileName"/>

r is not read until Send is called and the MIME type will be detected using https://golang.org/pkg/net/http/#DetectContentType

func (*MailYak) AttachInlineWithMimeType

func (m *MailYak) AttachInlineWithMimeType(name string, r io.Reader, mimeType string)

AttachInlineWithMimeType adds the contents of r to the email as an inline attachment with mimeType as the specified MIME type of the content. Inline attachments are typically used within the email body, such as a logo or header image. It is up to the user to ensure name is unique and the specified mimeType is correct.

Files can be referenced by their name within the email using the cid URL protocol:

<img src="cid:myFileName"/>

r is not read until Send is called.

func (*MailYak) AttachWithMimeType

func (m *MailYak) AttachWithMimeType(name string, r io.Reader, mimeType string)

AttachWithMimeType adds the contents of r to the email as an attachment with name as the filename and mimeType as the specified MIME type of the content. It is up to the user to ensure the mimeType is correct.

r is not read until Send is called

func (*MailYak) Bcc

func (m *MailYak) Bcc(addrs ...string)

Bcc sets a list of blind carbon copy (BCC) addresses.

You can pass one or more addresses to this method, none of which are viewable to the recipients.

mail.Bcc("dom@itsallbroken.com", "another@itsallbroken.com")

or pass a slice of strings:

bccs := []string{
	"one@itsallbroken.com",
	"two@itsallbroken.com"
}

mail.Bcc(bccs...)

func (*MailYak) Cc

func (m *MailYak) Cc(addrs ...string)

Cc sets a list of carbon copy (CC) addresses.

You can pass one or more addresses to this method, which are viewable to the other recipients.

mail.Cc("dom@itsallbroken.com", "another@itsallbroken.com")

or pass a slice of strings:

ccs := []string{
	"one@itsallbroken.com",
	"two@itsallbroken.com"
}

mail.Cc(ccs...)

func (*MailYak) ClearAttachments

func (m *MailYak) ClearAttachments()

ClearAttachments removes all current attachments.

func (*MailYak) From

func (m *MailYak) From(addr string)

From sets the sender email address.

Users should also consider setting FromName().

func (*MailYak) FromName

func (m *MailYak) FromName(name string)

FromName sets the sender name.

If set, emails typically display as being from:

From Name <sender@example.com>

If name contains non-ASCII characters, it is Q-encoded according to RFC1342.

func (*MailYak) HTML

func (m *MailYak) HTML() *BodyPart

HTML returns a BodyPart for the HTML email body.

func (*MailYak) MimeBuf

func (m *MailYak) MimeBuf() (*bytes.Buffer, error)

MimeBuf returns the buffer containing all the RAW MIME data.

MimeBuf is typically used with an API service such as Amazon SES that does not use an SMTP interface.

func (*MailYak) Plain

func (m *MailYak) Plain() *BodyPart

Plain returns a BodyPart for the plain-text email body.

func (*MailYak) ReplyTo

func (m *MailYak) ReplyTo(addr string)

ReplyTo sets the Reply-To email address.

Setting a ReplyTo address is optional.

func (*MailYak) Send

func (m *MailYak) Send() error

Send attempts to send the built email via the configured SMTP server.

Attachments are read when Send() is called, and any connection/authentication errors will be returned by Send().

func (*MailYak) String

func (m *MailYak) String() string

String returns a redacted description of the email state, typically for logging or debugging purposes.

Authentication information is not included in the returned string.

func (*MailYak) Subject

func (m *MailYak) Subject(sub string)

Subject sets the email subject line.

If sub contains non-ASCII characters, it is Q-encoded according to RFC1342.

func (*MailYak) To

func (m *MailYak) To(addrs ...string)

To sets a list of recipient addresses.

You can pass one or more addresses to this method, all of which are viewable to the recipients.

mail.To("dom@itsallbroken.com", "another@itsallbroken.com")

or pass a slice of strings:

tos := []string{
	"one@itsallbroken.com",
	"two@itsallbroken.com"
}

mail.To(tos...)

func (*MailYak) WriteBccHeader

func (m *MailYak) WriteBccHeader(shouldWrite bool)

WriteBccHeader writes the BCC header to the MIME body when true. Defaults to false.

This is usually required when writing the MIME body to an email API such as Amazon's SES, but can cause problems when sending emails via a SMTP server.

Specifically, RFC822 says:

Some  systems  may choose to include the text of the "Bcc" field only in the
author(s)'s  copy,  while  others  may also include it in the text sent to
all those indicated in the "Bcc" list.

This ambiguity can result in some SMTP servers not stripping the BCC header and exposing the BCC addressees to recipients. For more information, see:

https://github.com/domodwyer/mailyak/issues/14