• by Jess Nelson , January 14, 2016

One quarter of emails in the United States don't reach their intended recipients, according to a Return Path report that shows year-over-year email deliverability rates in 2015 fell as much as 4% worldwide to 79%, and by as much as 11% in the United States to 76%.

Despite the decline, SendGrid said Thursday it processed 225 billion emails in 2015, with a median delivery rate slightly above 98%. Considering that email’s high return on investment is impossible without the message first being delivered into a subscriber’s inbox, solving issues around deliverability is critical.

Victor Amin, data scientist at SendGrid, provided five recommended tips for increasing email deliverability rates in 2016 that marketers can immediately implement.

1. Quality Over Quantity

A simple opt-in feature guarantees your messages are being received by those who actually want to receive them, and properly formatted emails means they can be read. Poorly formatted emails, such as those with incorrect HTML coding, can also get caught in spam filters or may not render properly on mobile devices.

“Sending quality email that your subscribers want to receive is the basis of a great sending and brand reputation,” says Amin.

2. Consistency

Amin says email volume should be consistent and based on subscriber preference, since they are a key consideration for ISPs. “High-volume senders are always a red flag, especially when volumes are inconsistent,” he says.

Email marketers should consider sending approximately the same number of emails each week or month instead of inconsistent sending sprees. This means marketers may want to plan ahead before big events that might cause email volume to fluctuate, such as corporate events or consumer holidays.

3. Reputation Matters

Are a high number of your emails being labeled as spam or junk? This could be negatively affecting your sender score and email reputation, and thus negatively affecting your deliverability rates.

“Even a tiny increase in complaints can cause your email to be blocked by the ISPs,” says Amin. “Keeping your complaint rate very low and less than 1% of mail that is sent and accepted by the ISP is very important.”

Email marketers should also steer clear of spam traps -- email addresses activated by ISPs to catch spammers. Sending just one email into a spam trap can instantly set back reputation scores and cause deliverability problems, says Amin.

4. Keep Up-to-Date With Contact Information

A good reputation is impossible without low bounce rates, and Amin recommends marketers implement procedures to immediately remove email addresses that are returned by the ISPs because the account is no longer active.

“If a lot of your mail is bouncing back, it means your subscribers aren’t engaged and you’re not keeping up to date with them,” says Amin. “It also indicates that your list hygiene practices are not up to industry standards. This makes your email look like spam to an ISP and your email is unlikely to get delivered.

5. Stay Off of Email Blacklists

An email blacklist, also known as a DNS-based Blackhole list, is a database of set criteria that help ISPs determine whether an IP is sending legitimate email or spam. There are several blacklists that all have varying criteria that could negatively affect deliverability rates, including Spamhaus and Barracuda Reputation Block List (BRBL).

“Appearing on just one of the leading blacklists is enough to get you blocked by some ISPs,” says Amin. “Senders with low complaints, who don’t hit spam traps, and who send email consistently, generally don’t get blacklisted. However, if you do get blacklisted, having a good sending reputation will help convince the blacklist administrator to remove your IPs from their list.”