一般在mailwizz的后台地址：backend/index.php/misc/campaigns-bounce-logs 可以看到bounce的log，其中bounce type有3种：hard ，soft， internal ，看看他们的意思：
There are 3 types of bonce categories as follows.
Hard Bounces - A hard bounce means the email does not exist anymore on the target server, or it has been blocked/disabled or the target server does not exist, etc.
Soft Bounce - Unlike hard bounces, soft bounces can happen for reasons like server/account temporarily unavailable, not enough disk space to store the email on the server, or the receiving server is too busy, etc.
Internal Bounce - Your content is spammy, your IP/Server/domain listed in the blacklist, the range of IPs are listed in the blacklist, the link present in your email content is listed, subject lines are considered to be spam, etc. (Related to your email content or your IP/domain's reputation)
In email delivery the ISP (such as Gmail, Yahoo, Outlook etc) they will check each and every option starting from your subject line, your content, link present inside your email, your sending speed, the reputation of your IPs/domain.
Few ISPs are quite restrictive for excepting any emails such as Outlook, Hotmail of Live IDs.
As in the bounce message, you can see that they reject the email because of the few IPs (not your IPs specifically, but other IPs from the same network) already in their block list, hence they are not accepting it.
There any many email sender who did this kind of bulk mailing and OVH is a popular choice among them.
There are many types of the sender (few of them are the spammer too) so when most of them using their servers for these kinds of mailing, ISP (such as Outlook, Hotmail, Live) blocked the complete network instead of single IP.
There are many ISP and each and everyone have their own rules and regulation.
Unfortunately, this is something which can not be fixed since it will depend on those ISPs and which emails they want to accept and from which sender & from which network will be completely up to them.
These things are very common due to nature of this kind of mailing that few of the ISPs will be rejected and bounce back your emails, so it will be suggested to focus other ISPs which will still accept your emails and focus on your overall open rate.硬退回（Hard Bounces）——硬退回意味着电子邮件在目标服务器上不再存在，或者已被阻止/禁用，或者目标服务器不存在等。
软退回- 与硬退回不同，软退回可能由于服务器/帐户暂时不可用、服务器上没有足够的磁盘空间来存储电子邮件或接收服务器太忙等原因而发生。
内部退回- 您的内容是垃圾邮件，您的 IP/服务器/域名被列入黑名单，IP范围被列入黑名单，您的电子邮件内容中的链接被列出，主题行被视为垃圾邮件等。（与您的电子邮件内容或您的 IP/域名的信誉有关）
在电子邮件传递过程中，ISP（例如 Gmail、Yahoo、Outlook 等）会检查每个选项，从主题行、内容、电子邮件中的链接、发送速度、IP/域的信誉开始。一些 ISP 对接受任何电子邮件（例如 Outlook、Hotmail 或 Live ID）有严格的限制。正如在退回邮件中一样，您可以看到他们拒绝该电子邮件，因为他们的阻止列表中已经有几个 IP（不是您的 IP，而是来自同一网络的其他IP），因此他们不接受它。
有很多电子邮件发送者进行过这种批量发送邮件，而 OVH 是他们中比较流行的选择。发件人有很多种类型（其中有些也是垃圾邮件发送者），因此当他们中的大多数使用其服务器发送此类邮件时，ISP（例如 Outlook、Hotmail、Live）会阻止整个网络而不是单个 IP。
有许多 ISP，每个 ISP 都有自己的规则和规定。不幸的是，这是无法解决的问题，因为这取决于那些 ISP，他们想要接受哪些电子邮件以及来自哪个发件人和哪个网络的电子邮件完全由他们决定。
这些事情很常见，因为这种邮件的性质，很少有 ISP 会拒绝并退回您的电子邮件，所以建议关注其他仍然会接受您的电子邮件的 ISP，并关注您的整体打开率。