The problem with your getbizcreditinfo.com SMTP setup is that its SPF record contains include:getbizcreditinfo.com part. It creates an infinite SPF lookup loop and this fails the SPF check. The emails, sent from the domain with a failed SPF check will almost always end up in the Spam folder. You won't see it failed at Sendiio, because Sendiio only checks for the include:spf.sendiiosmtp.com part.
See the SPF guide I've added below for a full information.
Regarding the Sent and Delivered stats:
Sent stat indicates that the email has been processed by Sendiio. In most cases, you will see all broadcast emails to be sent out. If you see that the only a portion of a broadcast shows as sent, it can indicate that the SMTP account, which you've chosen to process those emails, has returned too many connection errors during the broadcast sending process, so Sendiio has aborted the broadcast sending procedure and could not send the rest of the emails.
Delivered stat indicates how many of the emails were accepted by the SMTP server. If the SMTP server has sent a successful status response to Sendiio for accepting the incoming emails, it will show as the delivered. If the email shows as undelivered, it either means that the SMTP server has returned an error status response, or did not even respond back to Sendiio in the allowed time limit at all.
SPF RECORD GUIDE
SPF record short overview
1. SPF (Sender Policy Framework) exists to set the list of SMTP servers (either their domain host names or their IP addresses), which are authorized to send the emails on behalf of your domain.
2. Your domain can have only a single SPF record. If your domain contains more than one, it will cause your emails to fail the SPF check by the recipient email services and they will end up in the Spam folder.
3. SPF record's type in your domain DNS settings should be TXT, not SPF. Some DNS control panels still allow to select the SPF record type. It's an obsolete, outdated format, and is not supported anymore.
4. If you ever need to add some additional SMTP servers to be authorized to send the emails on behalf of your domain, you need to add their information into the existing SPF record, instead of creating a new record (which would fail the SPF check by the recipient email services).
5. It is better to remove + before the include blocks, if any of them have it, it sometimes may cause conflicts.
6. Each use of a, mx, include, ptr, exists and redirect in the SPF record counts towards a DNS lookups limit of 10. If this counter exceeds this limit, it will cause a failure during the SPF record check by the recipient email services.
7. Using ip4 blocks does not count towards the DNS lookups limit of 10. So, if you have a direct IP address of the Outgoing SMTP server, you can use that instead of the include block.
SPF record example
In general your SPF should look like this (you can copy it and then replace the YOUR-OUTGOING-SMTP-SERVER- placeholders with the actual data):
v=spf1 +a +mx include:spf.sendiiosmtp.com include:YOUR-OUTGOING-SMTP-SERVER-NAME ip4:YOUR-OUTGOING-SMTP-SERVER-IP -all
Where:
1. include:spf.sendiiosmtp.com is a required part by Sendiio, without it your SPF record won't be verified by Sendiio.
A note: this is the only part of the SPF record that Sendiio can verify, when verifying the domain records. Your record may still be incorrect in terms of not pointing to the SMTP server, but Sendiio won't know about it. So, only because Sendiio shows this record as verified, it does not mean that it is automatically correct. You still need to check it yourself by this guide to see that it follows all the SPF rules and points to the correct SMTP server.
2. include:YOUR-OUTGOING-SMTP-SERVER-NAME is the Outgoing SMTP server name. You need to check the exact name of your SMTP server with your domain hosting support desk. This should be the same name, which you will then enter at SMTP account details, where you will need to specify the SMTP host name. This information may also be available at some hosting website documentation or may be present inside your domain control panel.
3. ip4:YOUR-OUTGOING-SMTP-SERVER-IP is the IP address of that Outgoing SMTP server above. Like with the OUTGOING-SMTP-SERVER-NAME, you need to check the exact name of your SMTP server with your domain hosting support desk, or this information may be covered somewhere in the hosting website documentation or your domain control panel.
Important
In a very rare cases where your web domain name matches the Outgoing SMTP server name (which normally should never happen), you need to skip include:YOUR-OUTGOING-SMTP-SERVER-NAME in your SPF record completely and only add ip4:YOUR-OUTGOING-SMTP-SERVER-IP.
How to verify your SPF record
After you've added or updated the SPF record and has given it some time to be updated on the Internet (it can take up to 48 hours sometimes), you can use this online SPF & DKIM records checker to see if it's visible on the Internet.
Domain name: your domain name, for ex. my-domain.com
DKIM Selector: sendiio._domainkey
Use the button Check SPF & DKIM keys to see the results.
You can also use MX Toolbox SPF Record Check to get a full report on a found SPF record, where you can see if it has any issues.
And always make sure that your domain has only one SPF record. If these SPF tools do not find the SPF record at all, then you need to investigate it with your hosting support, there's nothing we can do about that from our side.