Bounces
A bounce means an email could not be delivered. Repeatedly sending to bad addresses can hurt future delivery.
Overview
A bounce happens when an email cannot be delivered. Some bounces are temporary, such as a full mailbox or a temporary email delivery service issue. Other bounces are more permanent, such as an address that does not exist.
Hard bounces usually mean the address should not receive normal future sends. Examples include an address that does not exist or a domain that cannot receive mail. Continuing to mail bad addresses tells inbox providers that the list is not well maintained.
Soft bounces can happen for temporary reasons. A mailbox may be full, a receiving server may be temporarily unavailable, or your email delivery service may throttle traffic. The email delivery service may retry soft bounces before it stops trying.
Email delivery service event names can differ, but the meaning is the same: some delivery failures are temporary and some are final. When you review bounce events, check the failure reason before you group every bounce together.
Email delivery service webhooks are important because they let Mailrith receive bounce events and update subscriber status. Without webhooks, the email delivery service may record a bounce while Mailrith never receives the event.
High bounce rates often point to a subscriber-list problem. Old imports, purchased lists, typo-heavy forms, unverified signups, and stale addresses can all create bounces. Fixing bounces usually means improving list collection and cleanup, not rewriting the email body.
What to Do
- Set up email delivery service webhooks from Email Delivery Connections.
- After a send, review bounce events in Mailrith. If needed, compare them with bounce events in your email delivery service dashboard.
- When your email delivery service provides the failure type, separate hard bounces from temporary or soft bounces.
- If many addresses bounce, pause sending to that list and inspect where the subscriber records came from.
- Do not manually reactivate hard-bounced addresses unless the address owner confirms that the address is valid.
- Before you import an old list, remove obvious invalid addresses and send to a small test segment first.
- Use Suppression Lists and Subscriber Status so bounced addresses stay out of future normal sends.
What to Check
- Watch the bounce rate after imports, launches, and campaigns to old lists.
- Remove or suppress addresses that hard bounce.
- Check email delivery service webhooks if bounce events appear in the email delivery service dashboard but not in Mailrith.
- Do not retry a large failed send until you understand why the emails bounced.
- Use smaller tests when list quality is uncertain.
- High bounce rates can damage Sender Reputation and Spam Rate.
- Bounced subscribers should usually be protected by Suppression Lists and Subscriber Status.
- If bounces appear in your email delivery service but not in Mailrith, check webhook setup before you rely only on Mailrith's event count.
- If one domain bounces heavily, such as one company domain or mailbox provider, inspect the error reason before you suppress the whole list.
Fix Common Issues
Mail Records Do Not Prove a Mailbox Exists
An email checker found MX records for the domain. This proves only that the domain can receive mail somewhere; it does not prove that the exact inbox exists.
- Keep the address only if the subscriber provided it through a trusted source.
- Use normal subscriber activity, confirmation, or a successful send to increase confidence that the address is valid.
- After the first send, watch for a bounce from that address.
- Do not use SMTP probing as proof of permission.
Domain Without MX Records
An email checker found no MX records for the email domain, although the domain may still have address records.
- Before you import the address, ask the subscriber to confirm that the address is correct.
- Check that the domain is spelled correctly.
- If this is your domain, add proper MX records through the mailbox provider.
- Avoid sending at volume to addresses on domains that do not have normal receiving records.
Domain Cannot Receive Mail
An email checker found no MX, A, or AAAA records for the email domain, so the domain does not currently look reachable for email.
- Do not import the address as an active subscriber, and do not send to it as an active subscriber.
- Check whether the domain was mistyped.
- Ask the subscriber for a corrected address.
- If this domain belongs to you, fix DNS before you try to send mail to addresses on it.
Note
A hard bounce is a stop sign. Do not keep sending normal marketing email to an address that your email delivery service says does not exist.