smtp: SMTP functions

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SMTP functions for sending emails (electronic mail) by using SMTP (Simple Mail Transfer Protocol).

SMTP is an internet standard for email transmission across IP networks that are typically only used for sending messages to a mail server for relaying.

The SMTP functions support two ways of sending emails.

smtpSend, for simple short messages:

Advantages:

•Only the smtpSend function is needed.

•The function waits for the mail transfer to complete.

Disadvantages:

•The function waits for the mail transfer to complete.

•Only a short text message.

•No attachments.

smtpSendX, for advanced messages:

Advantages:

•Large text messages.

•Message text can be built over time.

•File attachments.

•Asynchronous mail transfer (depending on the situation, this can also be a disadvantage).

•Mail transfer progress can be monitored.

Disadvantages:

•Several functions are required to build and send an email.

The following sequence is required to make and send the email:

1.	smtpNew	To create the email.
2.	smtpAddText	To add text to the email message (repeatedly for large messages).
3.	smtpAddAttachment	To attach file(s) to the email.
4.	smtpSendX	To start sending the email.
5.	smtpAwaitCompletion	To wait for the mail transfer to complete (optional).
6.	smtpStatus	To monitor mail transfer progress (optional).

The following functions are used to access the SMTP interface:

	•smtpOpen	Opens the SMTP interface.
	•smtpClose	Closes the SMTP interface.
	•smtpSetConfig	Sets the SMTP configuration.
	•smtpGetConfig	Gets the SMTP configuration.
	•smtpSend	Sends an email.
	•smtpNew	Creates a new email.
	•smtpAddText	Adds text to an email.
	•smtpAddAttachment	Attaches a file to an email.
	•smtpSendX	Starts sending an email.
	•smtpCancel	Cancels a mail transfer.
	•smtpStatus	Gets the status of an email.
	•smtpAwaitCompletion	Waits for mail transfer to be completed.

The implementation of SMTP has the following limitations:

•The outbox can hold two emails simultaneously.

•All email addresses are limited to 40 characters and a single address.

•The message text of an advanced email is restricted to a maximum length of 4095 characters.

•It is possible to attach a maximum of one file to an email.

•A network interface connection must be available.