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[ Email Optimization ]

A Comprehensive & Concise Email Deliverability Guide


The following best practices are generally considered sound advice for any person-to-person email correspondence and are not necessarily specific to our service. These tips and guidelines are intended to reduce the possibility of your email ending up in your recipient’s spam folder, or worse, rejected by their email provider. The goal is to help you avoid the well-known mistakes that commonly trigger spam filtering in most modern email services and clients.


  • Use a reputable and well-known email client. This will ensure that the email you send will be properly constructed and communicated.
  • Things like providing HTML and text versions of the message content, properly constructed and formatted email headers, and adherence to specifications for sending email (SMTP) are fundamental to sending good mail.
  • Keep your message’s layout as simple as possible. Avoid complex formatting.
  • If you’re sending HTML email, ensure that it’s properly constructed. Things like missing/empty tags, poor formatting, and non-standard conventions are spam indicators.
  • Don’t insert active components (javascript, ActiveX, plug-ins) in your message. If you need rich media content, just link to a media-rich page on your web site.
  • Use personalized greetings/salutations. Generic salutations make your content more likely to appear as unsolicited mail to spam filters.
  • Do not use links that contain IP addresses. Using IP addresses is a huge red flag for spam filters.
  • If you link to other companies’ sites in your message content, ensure that they are reputable sites.
  • Be careful about using shortened urls in your message content. Shortened links are often used by spammers to mask the destination of the link; spam filters often flag messages with shortened links as spam.
  • Avoid using symbols for letters in words; spellings like “str@nge”, “|etters”, and “g00gle” in your emails are often classified as spam.
  • Do not overtly reference topics that are highly recognized as spam such as Rolex watches, medications, prescription drugs, or financial institutions.

Subject Line

Pay attention to your subject line. Avoid the following:

  • Punctuation (especially exclamations and question marks).
  • Using only capital letters.
  • Words such as “urgent”, “free”, “guaranteed.”
  • Text with spaces between every letter, such as “H e l l o.”


  • It is becoming preferable to avoid attaching files to your messages. Most cloud file sites now offer shareable links you can provide in your email (, Microsoft OneDrive, Google Docs, etc.). Since attachments are a common way of distributing viruses (especially for Windows users), filters are becoming more strict on attachments. Zip file attachments are a common example of this.
  • If you do send attachments, be sure they are named correctly and the spelling is correct. Also, choose a name that is simple and specific to the nature of the attachment.


If you need to send email to a larger number of recipients that falls within our sending limits, then here are some recommendations to ensure delivery both on our system and at other providers:

  • Follow all the person-to-person best practices for creating the your messages.
  • Ensure all recipients are end-user destinations.
    • Our platform is intended for person-to-person communications.
    • Ideally, these are people you already correspond with person-to-person.
  • Use DNS-based sender authentication records for your domains (SPF/DKIM/DMARC):
    • The more email you send, the more important it is that receivers can authenticate your email is from an authorized source.
  • Avoid ‘blasting’ emails to many people.
    • Tools like mail merge can allow for many messages to be generated/sent in a short period of time.

Email Lists

  • Ensure your recipient lists are current and accurate.
  • Do not use paid-for lists.
  • Sending emails to large numbers of invalid recipients is a clear indicator of spam. Also, mail providers and ISPs can use common invalid addresses as spam traps. Sending mail to these spam traps can result in your domain being blocklisted.

Opt In

  • Ensure that you’re only sending mail to users who specifically requested it.
  • Use confirmed opt-in practices when collecting email addresses for mailing lists to reduce the chances of your messages being considered unsolicited. Unsolicited email is more likely to be marked as spam by recipients, leading to you being flagged as a spammer by content filters.


  • Make sure that if you send email newsletters or communications to your customers, always provide them with a means to remove themselves from your mailing list.
  • Maintain a safe and reputable business website. It should include easy access to any privacy policies and contact information for your business.


  • Be sure that other companies you allow to include references to your business are reputable. If they send out spam and your company information is referenced in those emails, your domain could be flagged as being related to spam.
  • Conversely, be careful which domains/companies you reference in your emails. If those companies are already flagged for spamming activities, your email could be marked as spam or blocklisted for referencing those domains/companies.


  • Authenticate with Domain Keys Identified Mail (DKIM) – This will provide you with a consistent reputation across your domain, regardless of what IPs you send mail from.
  • Publish an SPF record – This will tell us which hosts can send messages from your domain.
  • Publish a DMARC record – Messages spoofing your domain will appear unauthenticated and therefore be rejected, depending upon your policy disposition. You can learn more at

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