Trouble e-mailing certain attachments? They could be blocked.

Have you ever been unable to send an e-mail, with attachments, from your web server? Have mail recipients told you that the message you sent did not arrive, or that it arrived but without the expected attachments? It could be that your mail server blocks certain attachments.

Some mail server administrators block the sending or receiving of attachments with specified file types. They block types of files that could potentially be harmful to recipients’ computers. For example, at my former web host administrators set Exim, the mail handler used in cPanel, to filter both outgoing and incoming mail. Exim blocked attachments of the following types:

ade    adp    bas    bat    chm    cmd    com    cpl    crt    eml    exe    hlp    hta    inf    ins    isp    jse    lnk    mdb    mde    msc    msi    msp    mst    pcd    pif    reg    scr    sct    shs    url    vbs    vbe    wsf    wsh    wsc

This was not a virus scan, and in fact the files’ contents were not scanned at all. The mail server blocked these attachments based solely on their file extensions, as such files were potentially harmful and used by viruses and other malware.

For you WebHostingBuzz clients, WHB does not block attachments on its cPanel servers. They find that attachment filters produce more complaints than not filtering.

One of my clients blocks many attachment types on their mail servers. Frustratingly, the server blocks many file types that are unlikely to be harmful. The workaround I used was to pack such files into a .zip file, which the client’s employees could receive. Another solution, if you face this situation, is to upload the files to a media sharing server and then send your recipient the download URLs.

If you’re having difficult sending certain file attachments to people, consider that they may be blocked. Choose a method that works for you.