Sending bulk e-mails with (big) attachments

We would like to send a bulk mail with an attachment (for instance a 500 kB PDF file) to all authors, how do we proceed?

(A German version of this article is available.)

You can send bulk e-mails with small attachments in ConfTool Pro, but it is usually not advisable to use attachments in bulk-e-mails, as:

• sending bulk e-mails with attachments takes quite long.
• many people have limited mailbox space and mails with attachments are more likely to be rejected due to "over quota".
• many people consider it "bad netiquette" to send bulk e-mails with attachments, because they also cause unwanted traffic for the receivers: maybe they do not want to download the attachment when you send it, as they are for instance on a mobile line (and this creates costs), or have a connection with low bandwidth (and they have to wait long for their e-mails to be downloaded).
• the risk that your e-mails will be classified as spam increases.
• some servers might even put the sending mail server on a black list (e.g. Yahoo), and the users will not receive the e-mail.
• if you find out that your attachment contains major typos or factual errors, you will have to re-send the bulk e-mail (with the attachment... ).
• the attachments cause considerable traffic, as every mail is sent individually. Example: 300 e-mails with 500kB attachment cause over 200 MB traffic (e-mail encoding makes attachments about 30% bigger).
• many people consider e-mail attachments as a security issue. In fact, malware is commonly distributed as an e-mail attachment. Therefore, if you send an attachment, never attach executable files or (ZIP-)archives. Even office files (Word, Excel) can include harmful macros. Currently PDF attachments seem to be rather safe.
• for the reason above, executable files such as files with the extensions .exe, .com, among others, cannot be sent via ConfTool. Furthermore, .doc files have been disabled, too, as many of these files are currently infected with macro viruses that use the Word application's own macro programming language. However, .docx files can still be sent because this file type cannot contain any macros. 

So what can you do?

Save the file on the main server of your conference and include a link to the file in the e-mail (for instance http://www.your-conference.edu/invitation.pdf).

If you currently don't have the option to upload files to your server, maybe have a look at (free) file sharing services like http://ge.tt/, https://wetransfer.com/ or https://send.firefox.com/ and send the link to your uploaded file.
Then the receivers can decide when to download the file, the download is much faster, and you can update the file if required.

Further advantages of this method:

• The link can be placed inline within the document text and can therefore provide more context for the reader.
  Attachments are always shown outside or below the main e-mail document.
• You can easily add several download links in an e-mail and each one has its own context.

You can also try to compress your PDF file by using tools like: easy PDF, I love PDF, Smallpdf or CleverPDF.