Deliverability is the likelihood of your emails reaching your Profiles' inboxes. You can have a large impact on your email deliverability — it's not just a technical issue, it's something you influence with every send. This article gives you the practical steps to keep your delivery rate high and your sender reputation strong.

Email deliverability is determined by several factors on both the sender's and receiver's side — including consent, authentication, sender reputation, content quality, ISP throttling, bounces, and spam filtering.

Delivery rate is calculated by dividing the number of emails delivered by the number of emails sent. A healthy list should achieve a delivery rate around 99% — 100% is almost impossible for any list of meaningful size. A delivery rate significantly below 99% typically signals poor list quality, missing authentication, or spam-trigger content.

When you hit "Send" in Apsis One, the email doesn't go straight to the recipient's inbox. It passes through several checkpoints — think of it like a package going through customs. At each stage, things can slow down, reroute, or even block delivery.

This is where the journey starts. Apsis One sends the email from a managed IP address via your private technical sender domain. The system checks authentication (SPF, DKIM) and applies tracking parameters. When your Email Report shows "Delivered", it means the receiving server accepted the email — not that it landed in someone's inbox.

The recipient's email provider (Microsoft 365, Google Workspace, a company's own server, etc.) accepts the email and then runs its own checks before placing it in the inbox. This is where delays most commonly happen:

Even after the receiving server accepts the email, it passes through spam filters, virus scanners, and reputation checks. These can add processing time, reroute the email to junk or spam, or hold it for review — all invisible to the sender. This is where your sender reputation, content quality, and authentication status determine whether the email is placed in the inbox, the promotions tab, or the spam folder.

Only after clearing all of the above does the email actually appear in the recipient's inbox. And even then, some email clients (especially Outlook desktop) don't always sync instantly — they fetch new mail on intervals, which can add a few more minutes of apparent delay.

Your audience quality is the single biggest factor in deliverability. Sending to Profiles who didn't consent, are inactive, or have invalid addresses damages your sender reputation and delivery rate.

Your Email Report contains three metrics that directly signal to ISPs whether you're a trustworthy sender. Ignoring them — or letting them creep up — is the fastest way to damage your deliverability.

A bounce means the receiving server rejected the email. Bounces fall into three categories:

Why it matters for deliverability: A high bounce rate tells ISPs your list is poorly maintained. Repeated sends to invalid addresses look like spammer behaviour. Keep your bounce rate as close to 0% as possible by maintaining clean, consented lists.

A spam complaint is recorded when a recipient clicks "Report spam" or "This is spam" in their email client. The complaint number in your Email Report reflects only Profiles who actively reported the email — it does not reflect the total number of emails that landed in a spam or junk folder (that's a separate, mostly invisible process).

Why it matters for deliverability: Spam complaints are the most damaging signal to your sender reputation. ISPs track complaint rates closely — Google recommends staying below 0.1% (1 complaint per 1,000 delivered emails). Consistently exceeding this threshold will result in your emails being routed to spam or blocked entirely. Common causes include sending to Profiles who didn't consent, sending too frequently, having a hard-to-find unsubscribe link, or sending irrelevant content.

An unsubscribe happens when a Profile clicks the unsubscribe link and confirms the opt-out. Unlike spam complaints, unsubscribes are a healthy signal — they mean the Profile found and used the intended opt-out mechanism instead of reporting you as spam.

Why it matters for deliverability: A visible, easy-to-find unsubscribe link actually protects your deliverability. When the opt-out path is clear, disinterested recipients unsubscribe cleanly instead of hitting the spam button. Never re-subscribe a Profile who has unsubscribed unless you have received explicit, new consent.

The content of your email affects whether spam filters let it through. Follow these guidelines to stay out of the spam folder:

Email authentication proves to recipient servers that your email is legitimate and not sent by someone impersonating your domain. It's one of the most important factors in deliverability.

Read more: Email Authentication – Safe Sending

Setting up a Custom domain for links and system pages adjusts URLs in your emails and system-generated pages (like the web version and unsubscribe page) to display your own domain instead of the default Apsis tracking domain.

When Profiles hover over or click a link and see your own domain, it builds trust and reinforces your brand. It also improves deliverability — some spam filters treat emails with unfamiliar third-party link domains as suspicious.

Read more: Custom domain — Setup and onboarding

If you're new to Apsis One or haven't sent to large audiences before, your private technical sender domain needs to be gradually warmed up. Sending a large volume immediately from a new or unused domain looks suspicious to ISPs and can result in your emails being throttled, sent to spam, or blocked.

Good data hygiene combined with a gradual warm-up ensures your technical sender domain builds a positive reputation over time.

The warm-up process applies to any account that intends to send to more than 10,000 recipients per day. Adjust the numbers below to match your target sending volume.

* For help with bad statistics, reach out to Customer Service and pause the warm-up process until the issue is resolved.

Follow up after each day by checking delivery statistics and open rates.