Excessive soft bounces in a campaign

What are the details of these soft bounces?

Hi Sanford, thanks so much for replying. I figured out the problem was my own stupidity. I had used incorrect information in one of the fields, which created a large number of soft bounces. Once I corrected the mistake, the remaining emails were delivered fine.

Yeah, it sometimes happened with me, here some tips to improve your soft bounces:

Soft bounces are often caused by temporary delivery issues that may be solved by the next email send. These issues include:
Your subscriber’s mailbox is full
Your recipient’s email server is down
The email message is too big.

1. Build and maintain a permission-based email list. This is a cardinal rule in keeping your email bounce rates low.
2. Use a preference center. By giving your subscribers choices and control over what types of information and how much email they receive from you, an email preference center can help keep your bounce rate low and ensure the success of your email campaigns.
3. Regularly and consistently send emails to your subscribers. By sending to your list regularly, you are not only less likely to see high bounce rates, but you are also likely to experience fewer spam complaints and higher subscriber engagement. People inevitably change their email addresses and abandon old addresses, which can result in email bounces. Contacting your subscribers regularly rather than sporadically will help prevent a high number of bounces occurring at once.
4. Keep track of your email deliverability and performance results. The longer you let issues such as high bounce rates and weak subscriber engagement go undetected, the more likely you will get a bad-sender reputation that will negatively impact your email deliverability.

Hope this will help you improve your subscriber's database.