This document offers some technical detail about what happens at selected stages of the completion of the Missive wizard.

Web server connections

Web server credentials are required so that the Missive server can make a number of deployments. A hostname, username and password are required. For security reasons, web server passwords are stored temporarily for immediate use, and then thrown away.

Both encrypted (SFTP/FTPS) and unencrypted (FTP) connections are supported, with encryption being preferred if the server supports it. In general, free hosts tend to only support FTP.

Host check

A simple script (host_check.php) is deployed to the web server that returns simple information about the web server. This helps Missive understand its capabilities, and whether it satisfies some required and optional modules:

It returns its data in a document like this:

  "ok": true,
  "modules": {
    "required": {
      "zip": true,
      "ctype": true,
      "openssl": true,
      "php": true
    "optional": {
      "escapeshellcmd": false,
      "popen": false
    "info": {
      "php_version": "7.1.11",
      "proceed": true,
      "warning_code": "no_sendmail"

The optional modules are needed for users who prefer Sendmail over SMTP. In the example above, both of the optional modules are not satisfied by the web server, so the no_sendmail flag is also returned.

This script self-deletes after it is used, as it is no longer required.

Email server credentials

A page is provided to record the email credentials (hostname, username, and password). These are in fact required only for SMTP, and if Sendmail is selected, the credentials can be skipped.

If Sendmail is not available, SMTP is fine - you’ll just need to get credentials from your web service provider. You can often just use a free email provider like GMail or Yahoo as well.

In a similar fashion to web server credentials, SMTP credentials are stored just temporarily in the Missive system. This means in the unlikely event that the system is cracked and the user database data is stolen, the value to a cracker is rather limited.

Of course, SMTP passwords must be stored on a remote web server permanently, so it is a good idea to use a low-value account. This means that if someone does get a hold of your email password, the worst impact is that the account may be used to send spam, rather than confidential material being obtained from your Sent Items folder.

App deployment

When deploying the form app on a web server, Missive will use a pre-compiled compressed file called It will also send an decompressor script called unzip.php, which is called remotely to unzip the package, and then self-deletes.

At this point, the remote app offers some limited remote control capabilities to make the deployment as easy as possible. There are two sub-systems here: “Investigator”, which is used to check and test the system, and “Mailer”, which contains facilities needed for the live form.

A brief list of these features are set out below:


Feature Description
port Check if an email server port is available
validate Performs a system self-test
exists Check if a PHP function is available
build Returns information about the version of the deployed system
email Sends a test email
erase Erases the whole app


Feature Description
field-list Lists the available fields so they can be rendered in JavaScript
hello Simple way of checking mailer script is available
email Send an email

Test email

Sending a test mail is done before the final configuration file is deployed to the remote server, so all the configuration is sent with the request. Test messages may only be sent to registered email addresses on the system.

The Missive app does need the SMTP password for this operation (unless another mail transfer system is specified), but as usual the password is deleted after the process finishes.

For SMTP requests, a log is available, to help debugging failing send operations.

Erase app

Users may remove the app from their server by activating the erase option, which will remove all files that were part of the original deployment. While this should not delete any new files added as part of a customisation, nevertheless, users are advised to take regular backups of their web space.

Configuration deployment

The final step is the resending of the configuration details so that the form behaves as designed. This sends an updated config.php containing, amongst other things, the contents of the emails sent when the form is completed.