About bounces (hard/soft)

What are bounces?

A bounce is an email that is returned to the Flexmail's servers because it for some reason could not be delivered to the recipient. When that happens, most servers include a bounce code with the message, which can give you some more context. These details can be found in your email campaign report. It's a good idea to keep a close eye on your bounce numbers to be sure your campaigns are reaching your subscribed contacts, and that you're abiding by spam laws.

Bounces can happen for many reasons:

Hard Bounce: The email address no longer exists.
Spam Complaint: The recipient marked your email as spam. Some email clients report this back to the sending server.
Soft Bounce, Auto Responder: The person is out of the office or the mailbox is full and not accepting emails, sending a code to the sender.
Transient, Message Delayed, DNS Error: There were problems connecting to the person’s mail server.
...

The different bounce types

Bounces fall into 2 basic categories:

Hard bounce

An email (and email address) is considered as a hard bounce when the email cannot be delivered, and we're pretty sure the next campaigns will probably not get delivered either. Hard bounces could for example be contacts that are no longer using that email address.

A bounce code that starts with a 5 is considered a hard bounce. For all these codes, you can assume those email addresses are considered invalid.
You can however be a 100% sure for email addresses that return with bounce code 5.1.1. We'll immediately move those email addresses to your blacklist with the status "hard bounce (email address doesn't exist)". If you would continue sending to these email addresses, there would be a considerable negative impact on your deliverability. That's because that behaviour could be interpreted as not considering database hygiene practices.

For all other hard bounce codes, we'll start counting the number of bounces for those email addresses. By default, we'll allow 3 hard bounces for consecutive campaigns.

Soft bounce

A soft bounce is usually transient. The campaign could not be delivered due to temporary problems. The contacts with a soft bounce will therefore not immediately be blacklisted. If an email address continues to soft bounce in additional campaigns, the address will eventually be considered a hard bounce and cleaned from your audience.

A bounce code that starts with a 4 is a soft bounce.

For example, a soft bounce can occur when the contact's mailbox is full or the mail server is not reachable by the recipient due to technical reasons.

In the general account settings under "Bounces" you can change the number of times an email address can soft bounce before it's considered "bounced out". By default, we put that number on 3.

If for some reason, a campaign could not be delivered to the receiving mail server, we will continue trying for the next 24 hours. If a campaign could be delivered to the receiving mail server, and got a bounce, we will not continue trying, since we received a bounce for this campaign.

The limit that has been set for the number of times a campaign can bounce (hard of soft bounce) applies to consecutive bounces with the same bounce code.

Support tip
Under your Campaign results > Deliveries, you can find more details on the bounce codes in that campaign and their meaning.

What you can do about bounced emails

Understanding which emails bounce will help you react proactively. For instance, if important emails are bouncing to a customer, you can notify them to update their profile. Bounces also help you learn more on the quality of your database.

There are occasionally cases in which valid email addresses will hard bounce.

False positives

In some cases an email might hard bounce, but still be valid due to the way the server rejected the message. We've also seen some Telenet servers that incorrectly send a 5.1.1 bounce codes, when in fact they're another problem occurring. If you feel an email was bounced incorrectly on the receiver's end, you can contact us through support@flexmail.be.

Address Change

If an address change is requested, it's best to contact those subscribers individually to ask for a new email address. You can then edit the subscriber's information in your own database to make sure your list is up to date.

Spam Complaints

A spam complaint is recorded when a subscriber clicks "This is Spam" or "Mark as Spam" in email clients like Gmail, Hotmail and other similar clients.

While you should not have any spam complaints, they do happen. Once a spam complaint is recorded, Flexmail will blacklist this address and will not let you reactivate it. In the email industry, spam complaints are a clear metric to determine abuse and poor sending practices. It’s important that we take these reports seriously to ensure the best delivery for all of our customers. That's also the reason why you cannot remove them from the blacklist yourself.

If the recipient reaches out to you or your sender and wants to receive emails again, contact us at support@flexmail.be and let us know to reactivate the recipient's address.

Spam Notification

This means that your content was rejected by a mail server. This could be due to rigid corporate policies in place on the receiving mail server or some bad choice of words in your email that are getting flagged by spam filters.

Spam Notifications need to be resolved on the receiving mail server side, specifically with the spam filter settings for the domain you are sending to. To resolve the blocks, contact the recipient through another channel and ask them to ask their IT team or mail administration team to whitelist either your sending domain or Flexmail's sending IP addresses in their spam filter settings.

ISP Blocks

A block usually means that our IP address or server was rejected from the receiving mail server. We constantly monitor delivery and reputation to prevent this.

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