A successful cold email campaign doesn’t start with the wording or choosing the right audience. The technical setup is at least as important: your emails can only be delivered reliably if your sending domain, email account, and campaign settings are configured correctly.
Wholix already handles important safeguards for you. These include fixed sending limits, automatic bounce processing, and verification of the leads provided through Wholix. However, factors outside Wholix’s control can also affect your deliverability, such as your domain’s DNS settings, your email account’s reputation, your signature, or lead lists you uploaded yourself.
So if your open rate suddenly drops, lots of emails bounce, or messages end up in the spam folder, don’t immediately focus only on changing the copy. Work through the following points step by step.
A low open rate can have several causes:
Emails are rejected by the receiving server and bounce.
Emails are delivered but end up in the spam folder.
Emails reach the inbox but aren’t opened.
Opens aren’t tracked reliably for technical or privacy-related reasons.
So don’t look only at your open rate. Also check bounces, replies, unsubscribes, and error messages from your email provider.
Open rates are now only a rough guide. Privacy features and technical image proxies can trigger opens automatically or prevent them from being measured. Replies, positive feedback, bounces, and booked appointments are usually more meaningful when evaluating your campaign.
Test it directly: Send a typical email from the affected mailbox to the unique test address provided by Mail-Tester. You’ll then receive feedback on authentication, spam signals, content, and possible blocklist entries.
The most important technical requirements for sending email are set through your domain’s DNS settings. Check whether SPF, DKIM, and DMARC are present and configured correctly.
The SPF record specifies which servers are allowed to send emails on behalf of your domain. All sending services you actually use must be authorized.
A domain should have only one SPF record. If an SPF record already exists, additional sending services usually need to be added to it. Don’t simply create a second SPF record.
Test SPF: Enter your sending domain in the free SPF Record Check from MXToolbox. The tool shows you the published SPF record and flags common errors.
DKIM adds a digital signature to outgoing emails. This allows the receiving server to check whether the message was actually sent through an authorized service and was not altered during transmission.
DKIM often needs to be not only added to DNS, but also enabled with your email provider. To check it, you’ll usually need the so-called DKIM selector. You can find it in your provider’s settings or instructions.
Test DKIM: Open the MXToolbox SuperTool and search for dkim:selector._domainkey.deinedomain.de. Replace the selector and domain with your own values.
DMARC specifies how receiving servers should handle emails that fail SPF or DKIM checks. DMARC also helps you detect misuse of your domain.
It’s not enough for a DMARC record to exist. The domains used must also be correctly aligned with the visible sender domain. This is known as “alignment.”
Test DMARC: Enter your domain in the free DMARC Check from MXToolbox. There you can see whether a DMARC record was found and whether there are any common configuration errors.
The specific DNS values vary by provider. So always use your provider’s current instructions when making changes, for example those from Google Workspace, Microsoft 365, IONOS, or your hosting provider. Don’t copy DNS records from another domain without checking them first.
After making a change, it may take some time for the new DNS values to become active worldwide. So check the settings again after updating them.
Even with correct DNS settings, the problem may lie directly with the email account. So check:
Is the email account still connected in Wholix?
Are the username, password, or app password still valid?
Was a security check or block triggered by the provider?
Are there any warnings or sending restrictions from the provider?
Was the domain or account set up only recently?
Also send a regular test email directly from the connected mailbox to an external address. If this message bounces or ends up in spam, the cause is probably the email account, domain, or provider—and not exclusively the Wholix campaign.
Test your domain and mail server: Enter your domain in Google Admin Toolbox – Check MX. The tool finds common errors in MX and DNS settings. It can also be used if your domain isn't registered with Google.
A large, cluttered signature can make the email unnecessarily complicated and generate additional spam signals. Use only the details that are truly necessary whenever possible:
First and last name
Position and company
Phone number, if required
Company website, if useful
Legally required information
Avoid where possible:
large logos and banners
multiple images or social media icons
long promotional texts
many different links
tracking or redirect links without a clear purpose
shortened links from public URL shorteners
unnecessary awards, seals, or quotes
The more streamlined the signature is, the more natural the message feels. Still, be sure to include the legal information required for your company.
Test your signature: Send an email with your complete signature to Mail-Tester. Test exactly the version you also use in your Wholix campaign.
Cold emails usually work best when they’re structured like a regular personal business email. Keep the first message especially concise:
no large images or graphics
no embedded videos
no file attachments in the initial contact
as few links as possible
no overloaded HTML design
no conspicuous fonts, colors, or formatting
File attachments and lots of external content not only increase technical complexity. They can also arouse recipients’ suspicion. It’s better to send presentations, PDFs, or further information only after the person has shown interest.
Test your email: Send the complete campaign text, including subject line, links, formatting, and signature, to Mail-Tester. This lets you check not only your domain, but the exact message that will be sent later.
Wholix has strict sending limits. This prevents a single email account from being overloaded indefinitely or getting “burned out” by accidentally sending too many emails. Wholix monitors and limits the permitted volume.
These limits are an important safeguard, but they don’t replace responsible sending practices. Email providers assess not only the total number of emails, but also sending history, fluctuations, recipient responses, and domain reputation.
So even with Wholix limits in place, keep the following in mind:
Start new or long-unused accounts with a moderate volume.
Don’t increase volume unnecessarily quickly.
Distribute your emails as evenly as possible.
Don’t start several campaigns at the same time through the same account without a good reason.
Keep an eye on the total volume of all ongoing campaigns.
Don’t automatically use the full technically available maximum.
Wholix prevents you from exceeding the configured hard limits. However, good deliverability doesn’t come from using every available limit to the fullest. Send carefully and use your judgment.
Check your reputation: Register your domain for free with Google Postmaster Tools. With sufficient sending volume, you can monitor your Gmail reputation, spam complaints, authentication rates, and delivery errors there, among other things. For new domains or low volume, data may not be available yet.
If an email bounces and Wholix detects the bounce, the affected recipient address is automatically blocked. Wholix then stops sending any further campaign emails or follow-ups to that address. This prevents invalid or unreachable addresses from being contacted repeatedly and further damaging your email account's reputation.
Not all bounces have the same cause:
A hard bounce usually means the address is permanently invalid or unreachable.
A soft bounce can occur temporarily, for example, when a mailbox is full or the receiving server has a temporary restriction.
A block or policy message can point to missing authentication, a poor reputation, your sending behavior, or the content.
Automatic blocking protects your account from sending further emails to the affected address. Still, you should check the specific error message if several addresses bounce within a short period. A high number of bounces can point to a bigger problem with your domain, your email account, or one of your own lead lists.
If you get many bounces, test: First, check your domain with Google Check MX and then send a test email to Mail-Tester. If no technical errors show up there, next check where your recipient addresses came from and whether they're up to date.
Leads that you buy through Wholix or receive from Wholix are technically checked and verified before being provided. This reduces the risk of invalid email addresses before sending.
However, verification can never guarantee that an address will remain reachable indefinitely. Employees may leave the company, mailboxes may be deactivated, and receiving servers may change their settings. If a verified address still bounces later, Wholix's automatic bounce block will take effect.
If you upload your own lead lists to Wholix, you are responsible for ensuring that the email addresses they contain are up to date, correct, and suitable for sending. Wholix cannot guarantee that addresses collected externally or some time ago are still valid.
Before uploading, check in particular:
Are the addresses current and verified as recently as possible?
Does the list contain obvious typos or invalid domains?
Are former employees or outdated contacts included?
Are there duplicate records?
Does the list already contain unsubscribed or objecting contacts?
Are many addresses classified as “Catch-all,” “Unknown,” or risky?
Remove invalid, outdated, and risky addresses before importing. A large, unverified list is no more valuable than a smaller, clean list—and it can even significantly harm your deliverability.
Test individual addresses: You can check individual addresses for free with the Hunter Email Verifier. For larger lists, you should use a professional bulk verification service before uploading. Keep in mind: Even a positive result cannot completely rule out a later bounce.
Email providers evaluate more than just technical settings. Recipient behavior also plays an important role. If many people delete your messages, mark them as spam, or react negatively, your domain reputation can decline.
Therefore, every campaign should:
have a clear connection to the recipient or the company,
address a genuinely relevant problem,
not use a misleading subject line,
not pretend to have a personal relationship that doesn't exist,
provide an easy way to stop receiving further messages,
promptly honor unsubscribe requests and objections.
Large email providers have additional requirements for unsubscribe options in marketing and bulk emails. Depending on the sending method and volume, a technical one-click unsubscribe header may be required in addition to a visible unsubscribe notice.
Check spam complaints: If your domain sends a sufficient volume of emails to Gmail recipients, you can monitor the reported spam rate in Google Postmaster Tools.
Links can affect deliverability—especially when they lead to domains with a poor reputation or pass through suspicious redirect services.
Our recommendation for the first cold email:
Use no links if possible, or at most one relevant link.
Link only to trustworthy, working HTTPS websites.
Avoid public link shorteners.
Don't use unnecessary redirect chains.
Check whether the linked website is accessible, secure, and professional.
Open and link tracking can also change the technical structure of a message. If you suspect deliverability issues, a controlled test without tracking can help narrow down the cause. Always change only one variable at a time.
Test links and content: Send the complete email to Mail-Tester. Also check your domain or the sending server's IP address with the MXToolbox Blacklist Check.
If deliverability suddenly gets significantly worse, it may make sense to pause the affected campaign for a few days. This is especially true in the following cases:
an unusually high number of bounces,
blocks or warnings from the email provider,
a sudden, sharp increase in sending volume,
many negative reactions,
a significant drop in domain reputation.
However, taking a break alone does not automatically solve the problem. Use the time to check your DNS settings, account connection, recipient list, signature, and content. Then start again in a controlled manner and monitor how things develop.
While you're taking a break, check: Check the domain with Google Check MX, the reputation with Google Postmaster Tools and a complete test email with Mail-Tester.
If you change several factors at once, you won't be able to tell later what caused the improvement or decline. So proceed systematically:
First, check SPF, DKIM, and DMARC.
Then check the email account and any provider errors.
Check bounces and—if you uploaded your own leads—the quality of the lead list.
If necessary, reduce the number of concurrent campaigns or the sending volume.
Simplify your signature, links, tracking, and formatting.
Only then test the subject line, opening, and target audience step by step.
This lets you clearly distinguish technical causes from content-related causes.
Wholix already supports you with important safeguards:
Strict sending limits protect the connected email account from uncontrolled high-volume sending.
Detected bounces are automatically blocked and not contacted again.
Leads provided by Wholix are technically checked and verified in advance.
Contacts who have been stopped or blocked won't receive any further campaign emails.
You should still regularly check your domain's DNS settings, your email provider connection, your signature, your content, and any lead lists you uploaded yourself.
A good target audience and compelling copy are important, but they can't make up for technical problems. Successful cold emailing starts with a properly configured domain, a stable email account, controlled sending, and high-quality recipient data.
Wholix takes care of a large part of the technical safeguards: We set fixed sending limits, automatically block bounced addresses, and verify the leads provided through Wholix. However, you still need to take care when using your own lead lists and managing your domain and email provider settings.
If deliverability gets worse, take a systematic approach: Check the technical setup first, then bounces and data quality, and only then the wording. This will help you find the cause faster and protect your domain's reputation in the long term.
If you’ve checked all the points and problems persist, contact Wholix Support. Include the affected sender address, the campaign name, the approximate time period, specific bounce or error messages, and an example of an affected email if possible. This will help us identify the cause more quickly.
