Send emails through VB6 if no email client

Question

I have a VB6 app which is used by a large number of clients.

I need to allow the clients to be able to send emails to me. In the past I have done this using Microsoft MAPI controls. However, not all of them have an email client installed, since they use webmail instead.

Is there any other method anyone can recommend which would allow them to do this?

Answer 1

SMTP

You can use CDO for Windows to do this if we make a few assumptions:

• Your users are all on Win2K or later.
• The users will never be behind a firewall blocking SMTP or proxying all SMTP port use to a corporate server.
• You have an SMTP server that you have an account you can let the user-mails be sent with.
• You embed the server's address and account credentials in your program.

Sometimes using an SMTP server listening on an alternate port will address the second issue, but often such an alternate port is even more likely to be blocked.

SMTP is Dying

Abuse over time has made SMTP less and less viable for automated/assisted user contact. There are just too many variables involved in trying to open some sort of "clear channel" for SMTP communication as people work harder to fight spammers and such.

Today I would be much more likely to use either WebDAV or a Web Service for this. Both use HTTP/HTTPS which is more likely to get past firewalls and usually get by most proxy servers as well. WebDAV is often more "slippery" at this than Web Services, which more and more proxies are bocking. You can also use something more RESTful than SOAPy since the traffic "smells more like" user browsing to proxy servers.

WebDAV is a Clean Option

There are even free WebDAV providers offering 2GB of storage with a main and a guest user. The guest account can be given limited rights to various folders so some folders they might post your messages to, other folders they might get data from (read only folders), etc. For a paid account you can get more storage, additional users, etc.

This works well. You can even use the same hosting for program version files, new version code to be downloaded and installed, etc. All you need on your end is an aggregator program that scoops up user posted messages and deletes them using the main user/pw.

You still need to embed user credentials in your program, but it can be a simpler matter to change passwords over time. Just have the program fetch an info file with a new password and an effective date and have the program flip the "new" password to "current" once run on that date or after.

WebDAV support in Windows varies. From WinXP SP3 forward you can simply programmatically map a drive letter to a WebDAV share and then use regular file I/O statements against it, and unmap the letter when done. For more general use across even Win9x you can build a simple WebDAV client on top of XMLHTTPRequest or use a 3rd party library.

Web Services Have Higher Costs

Just to start with you have server-side code to write and maintain, and you have to use a specific kind of hosting. For example if you built it using PHP you need a PHP host, ASP an ASP host, ASP.Net an ASP.Net host, etc.

Web Services can also be more problematic in terms of versioning. If you later update your program to provide different information in these user contact posts you have to make another Web Service as well as changing both the application and the aggregator. Using WebDAV you can just make a "new format" folder on the server and have the new program post the data there in the new format. Your aggregator can simply pull from both folders and do any necessary reformatting into your new local database/message repository format.

This is merely an incremental additional effort though and a Web Service might be the way to go, even if it is just something written like an HTML Form GET/POST acceptor.

Answer 2

Although this question is for VBA you may find it of interest. Sending Emails using VBA without MAPI