Zérospam

The proliferation of spam and anti-spam solutions is beginning to affect email delivery. In fact, anti-spam solutions—particularly low-end filters—often block legitimate emails. Obviously, the more sophisticated the anti-spam solution is, the lower its margin of error is. But since you don't know if your recipients use good or bad filters, here are a few simple suggestions that will increase the chances that your emails will reach their destination.

1. Always write something in the subject line of an email. Emails that do not have subjects appear suspicious.
2. Don't send emails that have a title only. When a message's body does not contain any text, this single factor will cause the detection engine to consider the email suspicious.
3. Avoid the overuse of capital letters. For example, the subject line or the body of a message can contain a few capital letters, but if the entire message is in capitals or if the body text contains an entire paragraph in capitals, the email may be considered suspicious.
4. Use regular commercial messaging software such as Microsoft Outlook, Outlook Express, Mozilla Thunderbird or Sunbird, rather than less professional software such as IncrediMail, 3D Mailbox, etc.
5. If you send emails from a free account (Hotmail, Yahoo, Gmail, etc.), it is preferable to do so from the provider's Web interface. In other words, if you use Gmail, send your emails from the Gmail Web site and not from Outlook or another messaging software. Due to certain SMTP checks, emails from free addresses may be blocked unless they come from a server that belongs to these addresses' providers.
6. Do not send file attachments greater than 5MB, as they will be rejected by most ISPs. To send large emails, use the FTP service.
7. If you use a signature with an image, the size of the image must be relatively small (100 x 150 pixels) and the signature's text must not be incorporated into the image. If you do not follow these rules, your message may be misidentified as image spam by some filters simply due to this signature.

Senders who do email marketing or send emails to a large number of recipients should follow the practices recommended by the Task Force on Spam established by the Federal Government of Canada*.

General guidelines

• Marketing email should only be sent to recipients who have provided their consent to receive such information.
• Keep proof that your recipients have agreed to receive your messages.
• Use double opt-in (rather than single opt-in or opt-out).
• The originating server must have the correct time. To make sure it does, you can synchronize it to a time server via NTP.
• Check the status of your public IP addresses on public blacklists and the DNSBL.
• For your email marketing, use the services of a provider that specializes in sending mass emails. These experts know exactly how to prevent your emails from being rejected. As sending mass emails is their main source of revenue, they must, at all costs, ensure that their customers' emails reach their destination. If you do email marketing, you need their help.

The originating server must respect (E)SMTP specifications

• Your infrastructure must accept bounced mail messages and you must take the necessary steps to ensure that there are no further messages sent to these addresses.
• Control the flow of your outgoing email. Do not exceed 50 connections per minute on the same domain.
• Your SMTP HELO/EHLO must refer to a valid, existing domain name (see RFC 821, Section 3.5. and RFC 2821, Section 3.6.*).
• The sender's gateway must connect to the recipient's different MX servers in increasing order (see RFC 2821, Section 5.*) If possible, configure your server so that it makes frequent new connection attempts if it is unable to connect to a server.
• Do not use SMTP Pipelining.

Email content

• Marketing email must give recipients an easy way to opt out, for example, by means of a URL or box to check off. We also recommend that you include a valid telephone number in the email so that recipients can request that their name be removed from the mailing list. It is important to immediately implement opt out requests.
• If you use the same image (logo, signature) in your marketing emails as in your business emails, you run the risk that your business emails (which are more important than your marketing emails) may be blocked. Some recipients could report your undesirable marketing emails to DNSBL operators. A message fingerprint may then be developed to block your marketing emails. Your business emails would subsequently be blocked by your recipients' anti-spam solution if they add message fingerprints. Be careful when using signatures that contain graphic elements.
• You should also avoid including links to a Web site in your marketing emails if your person-to-person emails contain links to this same Web site.