Best practices for bulk mail senders and postmasters when sending to Yahoo/Gmail

Use email authentication such as DKIM

This will help us identify that the email is legitimately from you and, if you sign all your email, it will help us identify forgeries, too.

In addition, using dedicated domains for different mail streams (e.g., transactional messages vs. marketing emails) is also a recommended practice.

Segregate your mail streams by IP addresses and/or domains

Yahoo! Mail keeps reputation data about each IP address and domain you send from.

Consistently manage your lists

Pay attention to hard and soft bounces as well as inactive recipients. Persistent emails to these addresses are a surefire way to get your connections deferred.

If your messages are being blocked, look closely at any SMTP Reply Codes our mail servers are returning to you and be sure you're addressing the problem.

Send email only to those that want it

Spammers write to many people who don't want their mail, so our anti-spam filters are designed to identify that behavior. To avoid being perceived as a spammer, use an opt-in method of subscription for your mailing list.

Respect the User's Mailbox

If a customer entrusts an email address to you during a transaction or for a particular newsletter, they do not expect to receive unrelated messages, such as extraneous marketing emails, in the process.

Warning: Adding email addresses to other lists without their explicit opt-in is a guaranteed way to lose a customer's trust.

Honor the frequency of the list's intent

If customers believe they are signing up for a monthly newsletter but they start receiving messages on a weekly basis, such a practice will likely prompt users to label your messages as spam.

Use a consistent "From:" header address

Your domain name is an important element of your brand. Using it consistently helps us and your recipients to distinguish your email from spam.

Additionally, using a static From: address helps users who have set up filters to route messages to a specific folder.

Publish reverse DNS (PTR) records for your sending IPs

If there is no reverse DNS entry for your IP address, or if it looks like a dynamically-assigned IP instead of a static mail server, Yahoo! is more likely to downgrade its sending reputation.

Secure your mail servers

Ensure your mail servers are not open to abuse. If your servers act as "open proxies" or "relays," spammers may attempt to send their own mail from your systems.

Keep your software up to date with the latest security patches, and always filter user-generated content before sending it out, to help prevent spammers from using your resources and tarnishing your reputation.

Use common-sense settings

While we have not published guidelines for numbers of connections you can concurrently use, we ask that you treat our resources with respect. The more you take, the fewer there are for others, which may force us to defer your connections.

Monitor your sending reputation

Regularly check your sending reputation with Yahoo! Mail and Gmail to ensure that your emails are not being marked as spam.

Optimize your email content

Ensure that your email content is relevant, engaging, and free from spammy elements to improve deliverability.

Use feedback loops

Participate in feedback loops provided by Yahoo! Mail and Gmail to receive reports on emails marked as spam and take corrective actions.