Deliverability is about getting your email into the inbox, not just delivered to the mail server. This article explains how mailbox providers such as Gmail and Outlook decide where your email ends up, and what you can do to stay out of the spam folder.
How mailbox providers decide
Mailbox providers protect their users from spam, phishing and viruses with automated filters. Like a bank checking your credit score before giving you a loan, the filters check your sender reputation before accepting your email. Even if you aren't a spammer, you can look like one if your numbers are poor.
Your reputation is built from all of these together:
- List quality: sending only to contacts who asked for your email. See Healthy lists and permission.
- Bounces: addresses that don't exist or reject your email.
- Complaints: contacts who mark your email as spam.
- Spam traps and blocklists: see Blocklists and spam traps.
- Engagement: whether contacts open, click and reply, or ignore and delete your email.
- Authentication: whether your domain is set up with SPF, DKIM and DMARC. See Sender domain authentication.
Two settings help every sender: authenticate your sender domain and use your own tracking domain.
Send at a steady volume
Mailbox providers trust senders with predictable sending patterns. Send regularly, and increase your volume gradually rather than in sudden jumps. A new IP address or sender domain has no reputation yet, so providers limit how much they accept from it at first. Read Warming up sender domains and IPs before you start sending from a new domain or IP.
Content that gets delivered
Meet expectations
- Send the content and frequency your contacts signed up for.
- Offer a preference center so contacts can choose what they receive instead of unsubscribing from everything.
- Use your brand in the sender name and subject line, so contacts recognize your email at a glance.
Make unsubscribing easy
A contact who can't find the unsubscribe link clicks the spam button instead, and complaints hurt your reputation more than unsubscribes. Never ask contacts to log in to unsubscribe. If you send several types of email, let contacts choose which ones to stop. Symplify adds a one-click unsubscribe header to every email, so Gmail and other providers can show an Unsubscribe link next to your sender name. See Unsubscribe methods.
Keep your sender details consistent
Use the same sender name and address for the same type of email. Contacts learn to recognize you, and Gmail's sender guidelines recommend it. If you change your sender details, contacts may not recognize you and report the email as spam.
Use a reply address that someone reads
Avoid no-reply addresses. Replies are a strong engagement signal for mailbox providers, and they give you direct feedback from your contacts. To handle out-of-office and other automatic replies, forward the reply address to a mailbox with filtering rules.
Balance images and text
An email that is mostly images and very little text is one of the most common reasons legitimate email lands in spam. Spam filters can't read images, so they treat image-only email with suspicion. Enough text also helps contacts who don't load images.
Avoid public link shorteners
Spam filters check the reputation of every domain linked in your email, including images. Public link shorteners are also used by spammers, so their domains often have a poor reputation. Link to your own domain instead.
Don't write out URLs as link text
Symplify replaces your links with tracking links on your tracking domain, to measure clicks. If the visible text is a URL, for example www.yourdomain.com, but the link points to the tracking domain, spam filters can read it as phishing. Use descriptive text, such as "Visit our website", for your links.
Common myths
"If my IP or domain is blocked, I can just switch to a new one."
A new IP address or domain has no reputation, which providers treat with even more suspicion. Your sending habits also come with you, so the problems return. Fix the cause instead.
"Words like 'free' and exclamation marks send me to spam."
Today, filtering is mostly based on reputation. A good reputation usually outweighs individual words. Content still matters, for example if you reuse templates that other senders with a poor reputation also use.
"Deliverability is my email provider's job."
Symplify takes care of the sending infrastructure, but your reputation comes from your lists, complaints, content and engagement. Those are in your control.
"My complaint rate is low, so my email reaches the inbox."
Contacts can only complain about email that reaches their inbox. If your email goes to spam, your complaint rate looks low even when your reputation is poor. Some providers also count complaints only from active contacts, so your real rate may be higher than you think.
"Authentication guarantees the inbox."
SPF, DKIM and DMARC prove that the email really comes from you. They don't put you in the inbox on their own. They are, however, required by Gmail and Yahoo for anyone sending in volume, and your reputation is tied to your authenticated domain. See Gmail, Yahoo and Microsoft requirements for bulk senders.
"If I'm blocked, I can call the provider and ask them to let my email through."
Filtering is automated. Find and fix the cause, and your deliverability recovers over time. Where a provider has a delisting process, it runs through a web form. Contact support if you need help.