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Sending Messages With Gmailr

Source: vignettes/sending_messages.Rmd
sending_messages.Rmd

Constructing a MIME message

Text

First we will construct a simple text only message

text_msg <- gm_mime() |>
  gm_to("james.f.hester@gmail.com") |>
  gm_from("me@somewhere.com") |>
  gm_text_body("Gmailr is a very handy package!")

You can convert the message to a properly formatted MIME message using as.character().

strwrap(as.character(text_msg))
#> [1] "MIME-Version: 1.0\r Date: Fri, 30 Jun 2023 15:58:35 GMT\r To:"       
#> [2] "james.f.hester@gmail.com\r From: me@somewhere.com\r Content-Type:"   
#> [3] "multipart/mixed; boundary=d54e24aff3ed1f733aadf023f65f0e3f\r"        
#> [4] "--d54e24aff3ed1f733aadf023f65f0e3f\r MIME-Version: 1.0\r Date: Fri," 
#> [5] "30 Jun 2023 15:58:35 GMT\r Content-Type: text/plain; charset=utf-8;" 
#> [6] "format=flowed\r Content-Transfer-Encoding: quoted-printable\r Gmailr"
#> [7] "is a very handy package!\r --d54e24aff3ed1f733aadf023f65f0e3f--\r"

HTML

You can also construct html messages. It is customary to provide a text only message along with the html message, but with modern email clients this is not strictly necessary.

html_msg <- gm_mime() |>
  gm_to("james.f.hester@gmail.com") |>
  gm_from("me@somewhere.com") |>
  gm_html_body("<b>Gmailr</b> is a <i>very</i> handy package!")

Attachments

You can add attachments to your message in two ways.

  1. If the data is in a file, use gm_attach_file(). The mime type is automatically guessed by mime::guess_type, or you can specify it yourself with the type parameter.
write.csv(file = "iris.csv", iris)

msg <- html_msg |>
  gm_subject("Here are some flowers") |>
  gm_attach_file("iris.csv")
  1. If the data are already loaded into R, you can use gm_attach_part() to attach the binary data to your file.
msg <- html_msg |>
  gm_attach_part(part = charToRaw("attach me!"), name = "please")

Including images

You can also add use attached images in HTML by setting the Content ID feature of mime emails. This can be done by referencing the image via a <img src=cid:xyz> tag using the id argument of send_file(). The tag value can by any unique identifier. E.g. here is an example of including a ggplot2 image

# First create a plot to send, and save it to mtcars.png
mtcars$gear <- as.factor(mtcars$gear)

png("mtcars.png", width = 400, height = 400, pointsize = 12)
with(
  mtcars,
  plot(hp,
    mpg,
    col = as.factor(gear),
    pch = 19,
    xlab = "Horsepower",
    ylab = "Miles / gallon"
  )
)
legend("topright",
  title = "# gears",
  pch = 19,
  col = seq_along(levels(mtcars$gear)),
  legend = levels(mtcars$gear)
)
dev.off()
#> agg_png 
#>       2

# Next create an HTML email that references the plot as 'foobar'
email <- gm_mime() |>
  gm_to("someaddress@somewhere.com") |>
  gm_from("someaddress@somewhere.com") |>
  gm_subject("Cars report") |>
  gm_html_body(
    '<h1>A plot of <b>MotorTrend</b> data <i>(1974)</i></h1>
    <br><img src="cid:foobar">'
  ) |>
  gm_attach_file("mtcars.png", id = "foobar")

Uploading

Create Draft

You can upload any mime message into your gmail drafts using gm_create_draft(). Be sure to give yourself at least compose permissions first.

gm_create_draft(file_attachment)

Insert

This inserts the message directly into your mailbox, bypassing gmail’s default scanning and classification algorithms.

gm_insert_message(file_attachment)

Import

This imports the email as though it was a normal message, with the same scanning and classification as normal email.

gm_import_message(file_attachment)

Sending

Draft

gm_send_draft() sends an email using the draft_id of an existing draft (possibly created with gm_create_draft()).

my_drafts <- gm_drafts()

gm_send_draft(gm_id(my_drafts, "draft_id")[1])

Message

You can also send an email message directly from a mime object using gm_send_message().

gm_send_message(file_attachment)

Troubleshooting

Gmail API error 400: Mail service not enabled

It is possible to have a high-functioning Google account that does not have Gmail enabled. For example, your account might be fully operational with respect to Google Drive and yet have no mail capabilities. Such an account cannot be used with the Gmail API and therefore with gmailr. However, you will still be able to complete the gmailr authorization process via gm_auth(). The problem will only reveal itself upon the first attempt to use the API and it will look something like this:

 Error in gmailr_POST(c("messages", "send"), user_id, class = "gmail_message",  : 
  Gmail API error: 400
  Mail service not enabled

You can confirm the account’s lack of mail capability by visiting https://mail.google.com/mail/ while logged in. If you don’t already have Gmail, this link gives you the option of adding mail to your existing account or creating a new, mail-capable account.