With any email service & any set of contacts you will always have some mail end up in the spam folder. Every receiving ISP is using different spam filtering techniques and some ISPs utilize some unpredictable and creative ways of combating spam. So you will undoubtedly have some mail filtered at some point when sending email campaigns.
The good news is that it is not something you should dread or worry about. By following some pretty simple concepts you can dramatically reduce the chance of email being filtered.
Things you can do to improve your email delivery
Remove inactive contacts
If your email communications are wanted, major ISPs will deliver them. If you are sending to many inactive contacts who don't open your emails, ISPs will consider your mail “unwanted” and deliver it to the spam folder. It's very important to routinely cleanse inactive subscribers from your list or move them into segments that get mailed less often. We have several automation recipes to help with that. Our engagement management tool also makes it super easy to remove the people from your list who haven't opened in a long time. As a general rule, you should only be sending to contacts who have opened in the past 12-24 months (or less) if you want to have top-notch deliverability. On the same note, make sure you're constantly finding ways to add new subscribers to your list to combat the natural process of list churn. The older your data, the harder it is to deliver.
Focus on good, engaging content
If your content is engaging and valuable your contacts will open and your emails will be delivered to the inbox. Make sure you are sending content that your subscribers signed up to receive and that it stays fresh and interesting. If you repeatedly send purely promotional, hard-sell offers, you will see read rates lower and deliverability decline.
Review your signup process and try to think like a subscriber
What did your contacts expect to receive when they signed up? If you are sending content they didn't expect to receive they won't read it and will mark it as spam. Think about the language you use on your signup form and make sure it's clear about what people are opting in to receive. Also, make sure your email design is consistent. Don't change out your logo or template too often because this will confuse recipients and lead to spam complaints.
Send more targeted, triggered, personalized emails as opposed to batch and blast campaigns
It's a lot more likely for big batches of mail to be identified as spam, whereas one-off automation messages will almost always be delivered and will keep your contacts engaged and happy. At the most basic level, be sure you have a welcome message to greet your subscribers after they signup. When possible, send fewer, more personalized messages.
It's important to find the right sending frequency. If you send too often, your subscribers will get burned out and may unsubscribe or mark your email as spam. If you send too infrequently, you won't establish a good reputation. As a general rule, you want to contact your subscribers a few times a week, but that depends on the relationship you have with your contacts and the type of content you provide.
Pay attention to the spam filter testing before sending
This is an option on the summary step of creating a campaign. While it’s not truly predictable of your inbox placement for that campaign, this feature will let you know if it spots any major issues with your email that could affect delivery.
Don’t send a single graphic/image
Sending an email that only contains a graphic is a sure-fire way to have delivery issues. You should take the time to design an email with text and graphics - not just a single image. On the flip side, it's not necessarily better to send plain text emails. The general rule is to have a good, balanced mix of images and text. Also, make sure that your images are optimized in size: heavy images can trigger antispam and penalize the user experience.
Don’t use a free email address as your “from” email
Instead of using your free/personal email address such as @yahoo.com or @gmail.com, you should use an email address for the company or organization from which you are sending an email.
Pay attention to the links in your email
Spam filters check the URLs that you are linking to. If you link to a domain that has a poor reputation you will be penalized.
Don’t use link shortening services like bit.ly
Your links should be full links to the real URL. Link shortening services like bit.ly are used heavily by spammers. You can also be penalized if you use an outward-facing link like http://mypage.com/promo that links to a different page like http://mypage.com/offer-1. For the outward-facing text, it's better to use “click here,” a short descriptive sentence, or a button.
Send using a consistent “From” name and email address
We do not suggest changing your “From” details often. Keeping it consistent can help build your reputation. Take some time to think about what From Name will be the most recognizable to your recipients. It can be your company name, a figure in your company, or even something more unique. The more recognizable it is, the less likely people are to mark it as spam. The From Name is a very important part of establishing your brand.
Check your automations
If you have automations running, routinely do health checks. You may learn that certain contacts are getting 6, 8, 10 messages a day which is causing them to ignore everything and hurt your sending reputation.
Don’t test using the same phrase as your subject and email contents
If you send an email with a very similar subject and message body it will likely be filtered as spam. (An example would be having the subject set to “this is a test” with the body set to “this is a test”.) You'll also want to avoid using the same “to” and “from” email addresses. Sending an email where the “to” email address is the same as the “from” email address will most certainly be marked as spam.
Make it very easy to unsubscribe
A spam complaint is very bad for your deliverability, but an unsubscribe is not necessarily bad — it just indicates that someone no longer wants your mail. You should make it very easy for contacts to unsubscribe so that they are not encouraged to mark it as spam. Make sure your unsubscribe link is easy to spot and think about putting a second unsubscribe link at the top of your email.
Keep in mind that your primary focus should be to maintain a healthy list of contacts, send content they truly want, engage your contacts, and encourage them to interact with your campaign. If you keep your focus on these items great delivery – and deliverability – will follow.