Your campaign went out, and the bounce notices started piling up. Every hard bounce tells Gmail or your SMTP provider that you are mailing addresses you never checked, and enough of them can push your next emails into spam or get your account limited.
The good news: bounces are one of the most fixable problems in cold email. The cause is almost always the list or the sending pattern, and both are in your control.
Step 1: Pause the campaign now
Stop sending before you diagnose anything. Every extra email to a bad list adds more bounces to your sender history. Pause the active campaign and any follow-up steps still queued behind it.
If you send from several accounts, check which ones were used. You will want to give those accounts a rest from cold sending for a few days while you clean up.
Step 2: Read the bounce messages
Not every bounce means the same thing. Open a handful of the bounce notices and look at the reason. They fall into two groups:
| Type | What it usually says | What to do |
|---|---|---|
| Hard bounce | User unknown, address not found, domain does not exist | Remove the address permanently |
| Soft bounce | Mailbox full, server busy, temporarily deferred | Keep it, but retry later and drop it if it keeps failing |
| Policy or block | Rejected for spam, sender blocked, authentication failed | Fix your sending setup, not the list |
If most bounces are hard, you have a list problem. If many mention blocks or authentication, you have a sender setup problem. Sometimes it is both.
Step 3: Remove every hard bounce
Pull the bounced addresses out of the list and out of any other list or folder they appear in. Never mail them again. A common mistake is deleting them from one campaign, then re-importing the same CSV next month and bouncing them all over again.
Keep a simple suppression list: one file or folder of addresses you will never send to. Check new imports against it.
Step 4: Verify the rest of the list before resending
The addresses that did not bounce this time are not automatically safe. Run the whole remaining list through email verification before you send another step. Verification checks whether the domain accepts mail and whether the mailbox looks real, so you catch bad addresses before your sender does.
After verifying, sort results into three buckets:
- Valid: safe to send.
- Invalid: remove, same as a hard bounce.
- Unknown or catch-all: the server accepts everything, so it cannot confirm the mailbox. Send to these in small batches, or skip them if your bounce rate is already a concern.
In GetClient you can run verification on a saved list before it goes into a campaign, so the list and the check live in the same place and you are not exporting files between tools.
Step 5: Clean the obvious junk by hand
Verification catches dead mailboxes, but a quick manual pass catches things that still hurt you:
- Typos like gmial.com or .con endings
- Placeholder addresses such as test@, example@ or email@domain.com scraped from website templates
- Duplicates of the same address
- Role addresses you do not want, like noreply@ or abuse@
- Leads from old lists that might be a year or more out of date
The lead list cleaning checklist walks through this in order. If your list came in as a spreadsheet, see how to clean a CSV before importing so broken columns and stray spaces do not create bad addresses.
Step 6: Fix where your leads come from
Old purchased lists and copied spreadsheets decay. People change jobs, businesses close, domains lapse. The fresher the source, the fewer bounces.
Pulling leads live means the data reflects what is public right now. For local businesses, GetClient's Google Maps scraper searches by keyword and city at the moment you run it and collects emails found on the business's own website, which you can then verify before sending. Whatever tool you use, compare options in best lead generation tools with freshness and verification in mind, not just list size.
Step 7: Check your sending setup and volume
If your bounce notices mention blocks, rejections or authentication, look at the sender side:
- Authentication: make sure your sending domain has SPF, DKIM and DMARC records set up. Your email provider's help docs explain exactly how for their service.
- Volume: sudden jumps in sends from a new or quiet account look suspicious. Ramp up gradually. See how many cold emails per day for a sensible pace.
- Spread: if you have more than one account, split sends across them and use weekday send limits instead of blasting everything at once.
- Unsubscribes: honor them immediately. Mailing people who opted out invites complaints, which hurt you alongside bounces. Rules on consent and opt-outs vary by country, so check the ones that apply to you.
Step 8: Restart small and watch
When the list is verified and your setup is checked, resume with a small batch, perhaps a day's worth at a lower limit than before. Watch the bounces over the next day or two. A practical rule of thumb many senders use is to keep bounces in the low single digits as a percentage; if you see more than that, stop and check the list again before scaling.
Once it holds steady, raise volume step by step. Make verification a habit for every new list, not a one-off rescue. And while you are rebuilding, it is a good moment to tighten the emails themselves with better personalization using merge tags, so the clean list you worked for actually gets replies.