A suppression list is the set of recipients Mailercloud will not deliver to. Once an address is on the list, every future transactional send to it is rejected before it leaves the platform. Nothing is queued, and nothing reaches the mailbox provider.
Repeatedly emailing addresses that hard bounce or mark you as spam is one of the fastest ways to damage a sending domain's reputation. The suppression list stops that automatically, keeps a record of why each address was suppressed, and lets you manage the list yourself when a recipient asks to be removed or re-added.
Log in to your Mailercloud account.
Go to the API platform.
Select "Suppressions" from the left-hand sidebar.
The page lists every suppressed recipient, with the most recent addition at the top.
Each row on the page tells you one recipient's full story:
Recipient — the suppressed email address.
Reason — why it was suppressed. This is either "Hard bounced", "Spam complaint" or "Manual".
SMTP response — the receiving server's own message, shown for automatic suppressions. Manual entries show two dashes instead.
Source — how the address was added: Automatic, Added by user, API, or CSV import.
Date added — when the address was suppressed, shown in your account's timezone.
You do not need to configure anything. Mailercloud adds recipients to the list on its own in two cases:
Hard bounce — the mailbox does not exist or has permanently refused the message. The SMTP response is stored so you can see exactly what the provider said.
Spam complaint — the recipient marked your email as spam in their mailbox.
Soft bounces, deferrals and temporary failures do not suppress a recipient. Those are retried normally.
Note: The date shown is the date the bounce or complaint happened, so it matches the same event in your Activities log.
Use this when you already know an address should never receive mail — an unsubscribe handled offline, a role account, or a complaint raised directly with you.
Click the "+ Add Suppression" button, then choose "Add Manually".
Enter the addresses, one per line.
Click "Add Suppression".
The addresses appear in the list immediately with the reason "Manual", and take effect on your next send.
If you are moving from another provider, or you keep your own do-not-contact list, you can import it in bulk.
Click the "+ Add Suppression" button, then choose "Import CSV or TXT".
Drag your file onto the upload area, or click "browse" to select it from your computer.
Review the parsed addresses, then click "Upload file".
Use a .csv or .txt file with one address per row. A file that also contains other columns is accepted — only the email address is read.
Large files are processed in the background, so you can leave the page while the import runs. You will receive an email when it finishes, telling you how many addresses were added, how many were already suppressed, and how many rows could not be read.
Note: Only one import runs at a time per account. The import option stays unavailable until the current file has finished processing.
Three controls narrow the list, and they can be combined with each other:
Search — type any part of an email address.
Reason — filter by "Hard Bounced", "Spam complaints" or "Manual". Each option shows how many addresses it covers.
Date — limit the list to a date range.
You can also sort by "Date added" using the arrows in the column header, and page through the list from the first page to the last.
Click "Export" to receive the current list as a CSV by email. Any search, reason or date filter you have applied is included in the export, so you can export just one category if you need to.
Reactivating removes an address from the suppression list so that it can receive mail again.
Find the recipient using the search box or the filters.
Click "Reactivate" on that row.
The address is removed straight away, and the next send to it will be delivered normally.
Note: Spam complaints cannot be self-reactivated. Those rows show "Contact support" instead. The recipient has explicitly asked their provider to block you, so lifting the suppression is a support-assisted decision rather than a self-service one.
Everything on this page is also available over the API using your API key — you can search the list, add recipients, and reactivate them programmatically. This is the practical option if you keep a do-not-contact list in your own system and want the two to stay in step.
For endpoints, parameters and sample requests, see the Suppressions endpoints in the Mailercloud API reference.
When you send to a suppressed recipient, the message is rejected before delivery and recorded in your Activities log as a rejection, with the reason shown.
The API still returns a success response for the request itself, because suppression is a per-recipient outcome rather than a request failure. If a message has several recipients, only the suppressed ones are dropped and the rest are delivered as normal. Clean recipients are unaffected, and the check adds no delay to your sending.
Access to the suppression list is controlled per user role. If the Suppressions page is not visible to a team member, ask an account administrator to grant the relevant permissions:
View Suppressions — open the page, search, filter and export the list.
Manage Suppressions — add recipients manually and import files.
Reactivate Suppressed Recipients — remove recipients from the list.
If you have any further questions or need help managing your suppression list, don't hesitate to contact our support team through the chat widget in your account. We're here to help you make the most of Mailercloud's powerful email marketing features.
