A lot of people new to email marketing express concern about their mailings being delivered as spam or worse having their site shut down by ISPs.   Those are justifiable concerns.   Even if your subscribers are opted in and your mailings contain unsubscribe links couldn’t someone still report you as spam?   Well, yes, that could very well happen but if a lot of your subscribers are reporting your mailing as spam then that naturally casts you in a suspicious light with your ISP.   So does having half your subscriber list being reported as bounces.   That right there throws a red flag and is a reason to set up bounce management if you haven’t already done so.  Your ISP has the right to ask why  so many opted in subscribers have email addresses that bounced or were reported as spam.

Another equally frustrating situation when you are just getting started with your new email marketing service is when you discover that your brand new IP address is delivering  most of your mailings into people’s junk mail boxes.  Or you just checked the content of your mailing against spam assassin and you have a perfect score only to discover that mailings are not being delivered in subscriber’s inboxes.  For someone that doesn’t know what’s going on deliverability appears crude and arbitrary.  That’s because the metrics used to determine whether a mailing is or is not spam is unfamiliar to them.  You can learn more about increasing your delivery rate here and here.   Defining the vagaries of email delivery to an inexperienced marketer is like trying to explain credit scores to someone who is completely unfamiliar with the complexities of our credit system.   EmailCheck can let you know whether your mailing contains red flags in the content of the mailing itself so that you can make adjustments to the content of the mailing to increase deliverability.  This would increase the likelihood that your mailing will not be flagged as spam but that doesn’t mean that there aren’t other red flags, or metrics, that would.
You may remember what it was like to get your first credit card or you may be familiar with someone that couldn’t get one because they had no established credit history.  To lenders its risky to hand out credit to someone that lacks an established credit history.   You’ve probably heard the expression that no credit is worse than bad credit.  Likewise, if you’re gmail, hotmail, or yahoo, then you don’t want people that are using your service to receive emails in their inbox unless you are certain that they want to receive them.   If they do not know anything about the IP address that is being used to deliver your mailing then they are apt to treat it suspiciously.   That’s why the onus is on you to take steps to make the necessary adjustments to ensure that these email service providers know that you are sending legitimate permission based mailings.   You can learn more about the adjustments you’ll need to make here and here.
It goes without saying that a person with a damaged credit due to a history of delinquent payments is going to have just as hard of a time getting a credit card.   Likewise, your from sender reputation will make it impossible to ever have a mailing delivered in a person’s inbox if your mailings are continually being reported as spam.  There may be instances where a person that subscribed to your mailing reports you as spam even though they opted in and confirmed their subscription to your newsletter.  If this happens as an exception rather than a rule then this shouldn’t effect your ability to deliver mailings too much.   One thing you could do is join feedback loops with the various email service providers so you can find out when this is happening and if necessary make the proper adjustments.
The best advice I can give you is to learn as much as you can about email marketing best practices and apply them to your email marketing service.   Over time your from sender reputation will increase in much the same way as a person who acts responsibly with their credit will increase their credit score over time.