MaxBulk Mailer fully supports attachments but except in very particular cases I would recommend not to send attachments as part of a bulk email campaign. I mean all of them, whatever they are, PDFs, Word files, Excel files and even pictures. There are several reasons for that but I will talk about the most important ones (in my opinion) for you and your recipients:
- Message size and delivery speed:
If you add attachments to your message you have to be very careful about the total size of the files, especially when sending individual messages (default) because you will send as many times that size during the delivery. That means sending a 250 KB attachment to 1,000 recipients will generate 250 MB traffic! As SMTP servers use to give around 2KB/s bandwidth per client, your delivery will take up to 35 hours to complete!
If you are like me, you are getting more and more spam with attachments. There is a real proliferation of such messages. If you don't know the person sending you the email, you don't open the file, even if you are curious. You just delete it. Indeed the opening of an attachment may potentially infect a computer so your recipients have to really know who you are. As an example, even a PDF file may launch any command on the operating system, after user confirmation (popup message). Different command lines may be specified for Windows, Unix and Mac. A PDF file may also contain attached files, which can be extracted and opened from the reader. That may be used to hide malicious executables in order to bypass some antivirus and content analysis engines.
- Server firewalls tempering / virus checking:
There are servers, especially corporate servers whose firewalls will almost universally block various types of email attachments. Typically they do it based on a combination of simple type matching rules (.exe, .pdf...), some heuristic checking such as sourcing or destination based on feedback of subscribed blacklists or virus checking. It is not always the firewall that does this, it can be a plugin or add-on device to the email gateway. Various companies sell specialized devices. Good ones, will notify the recipient and allow them to approve or disapprove the receipt of the attachment. Some others just drop them, even PDFs...
- Your recipients may not like attachments:
There are people that don't like to receive attachments directly in their mailbox. Maybe because of the message size or maybe because they have a slow internet connection, they like to have the choice to download your files or not.
So, in conclusion and as I said before, better avoid sending attachments, better make them available online uploading them to your web site. You can then add links to your message so your subscribers only have to click on those links to download the files. I believe it is the best method.
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