This is an issue with the recipient rather than your set up.

In this case you would contact the recipient directly and try to find a resolution for this.

This is also an issue with the recipient.

Again we recommend you contact the recipient, notify them of the issue, pointing them to their internet provider initially.

If you have a bad domain this is usually linked to your activity on that domain.
Spam related or malicious activity will cause your domain to be classed as "bad" and will eventually become blacklisted.

To resolve this issue you need to carefully examine your domain activity and eliminate any suspicious, malicious, or spam like activities.

This usually occurs because the email address of the recipient no longer exists.

The quickest resolution is to determine if the email address is still relevant i.e. if the recipient is still a member of that company. If they aren't then choose another member of that company to email.

Unfortunately this can be a long winded issue to resolve unless it is explicitly obvious.

First check your email design, both HTML and Text version. Does it resemble a spam email? Is there any HTML that has been made to match the background so it is "not visible"? Are there any unsafe links?

Then check your Email set up. Is the domain being used a reputable domain? Is the alias sensible?

This is relatively simple to resolve.

Find a recipient from the same company to send to. Or ask that contact for any alternative email address to send to.

Previous attempts of sending an email to the recipient in this case have failed.

Your best action is to re-send when the sending queue is less saturated.

This issue requires first contacting the administrator of your server to identify any issues.

If this is not fruitful then we recommend liaising with the customer directly to solve this issue.

This is usually due to spam policy.

You will need to check that your email does not contain any spam related content.
If the issue still persists then contact the server administrator for their advice.

Again this is an issue you will need to contact the server administrator for to resolve.

If someones inbox is full you will have to find an alternate email address to send to or a different contact in that company.

You will have to again contact the server administrator and explain the issue, as well as with your internet provider so they can try and locate the problem.

Again this is content related.

You will need to check that your email design is not spam like, checking links, images, font/background colours, and all aspects of your email design.

Again this is design/content related.

A certain combination of factors in your email are causing it to be treated as like a virus. Therefore you need to look at your design, identify any common phrases which are seen typically in spam emails and remove them. Find alternatives to certain words or layouts which appear virus like.

Unfortunately there isn't much you can do in this situation apart from the generic checks.
The reason cannot be identified so it is impossible to know the cause.

Your domain has been blacklisted! This shouldn't happen if you send out professional, good quality emails and don't use the domain for suspicious activity.

However if this does happen there is a resolution. Find out where your domain has been blacklisted i.e. Spamcop.
Once you have found the source, request a de-list. This process may be different for each blacklist website.

It may take a week or two but once you have been de-listed you will be able to use your domain to send emails again.

However, if it is denied a de-list then it means you cannot use that domain as it the listing is to severe. But this isn't a common issue.

This is also linked to your domain. If you have been sending out emails which are considered spam like then your reputation will decrease.

A few factors affect your domain reputation:

1. The age of your domain. The first several weeks after your domain is sent up your domain will automatically be deemed suspicious, so the younger your domain the more likely it is that it is classed as suspicious initially. We suggest warming up your domain using batch sending, preferably not sending thousands of emails out straight away.

2. Its classification. Ideally your domain should be classed to your industry. For example, if you are a bank you would be classified as finance, the same goes for your domains relation to your company.
    Typically dating and gambling classifications on a domain are less reputable as they are more likely to send out spam.

Usually when your email has been reported it is because it was moved into the recipients spam folder.

Again check your content to ensure that your design is up to scratch.

The email recipient has challenged whether you are a robot or not. Usually this is a simple task of confirming you are not a robot, as a lack of response causes the bounce.