Email deliverability into the inbox depends on several factors.
These factors may include: your server reputation , your domain reputation, your email subject, your email content, the recipient's email server, the recipient's firewall, the recipient's email client.
A soft bounce is an email message that gets as far as the recipient's mail server (it recognizes the address) but is bounced back undelivered before it gets to the intended recipient. A soft bounce might occur because the recipient's mailbox is full, the server is down or swamped with messages, or the message is too large.
There will be soft bounces due to factors such as mailbox being full, mail delivery delayed by server, out of office autoresponders.
A hard bounce is an email message that has been returned to the sender and is permanently undeliverable. Causes include invalid addresses (domain name doesn't exist, typos, changed address, etc.) or the email recipient's mail server has blocked your server.
There will also be hard bounces due to invalid emails due to people changing jobs, etc.
Do note that for each email list that we send, we provide additional emails to buffer for invalid emails.
We provide a 1 for 1 exchange for all hard bounces. To do so, please email us with your order number and attach the list of emails which have experienced hard bounces (in csv format)