The primary question is, "How can I be sure everyone gets my emails?" the answer is: "you can't be 100% sure", but you can do a lot to increase your ability to pass your emails through the many spam filters that everyone now uses.
In fact, the term "email deliverability" means the ability of your mail system to successfully deliver your emails to the recipient's mailbox without being blocked by the numerous antispam systems whose purpose is to block unwanted emails.
The whole global email and filtering system is based on compliance with certain rules and on reputation and therefore it is important to continuously check your reputation level on the internet.
A fundamental reputation management system are the BLACKLIST, i.e. lists of IP addresses, kept up to date and made available by a series of servers that can be consulted by anyone, in which the IP addresses that are the source of spam are listed.
MOST USED BLACKLISTS
IP blacklists are a global system for sharing IPs that send spam, once these IPs have been identified they are shared with all spam filtering systems so that emails from these IPs are blocked, it is therefore important that your IP is not present in these lists and if it is, understand why it was reported.
There are many IP blacklist management systems, some are very common and used by many spam filtering systems others less known and used only in some geographical areas, in this document we want to list the most common systems that you can consult manually to check if yours mail server has for some reason been blacklisted.
You can manually check the reputation of your IPs used by your SMTP server to send by directly accessing the links listed below.
Symantec Black List:
Sendescore (requires registration):
Talos reputation center:
Barracuda Central Blacklist:
Trendmicro Reputation Services:
Cyren Reputation Check:
MX toolbox blacklist check:
Proofpoint IP reputation:
NiX IP reputation:
If from the blacklist check above it appears that your IP is in the blacklist, you must request delisting, the delisting procedure varies according to the list so there is no standard procedure but you must follow the procedure provided for the specific blacklist, therefore depending on the blacklist follow the instructions provided (open a ticket or other procedure).
Of course, a pre-condition to be delisted is that of not sending spam emails anymore, but if the delisting request is frequent and repeated, the waiting time will be longer and more difficult to obtain the delisting.
The following are the most common delisting procedures:
To be delisted from office 365 you need to follow this link: https://sender.office.com/ here you will be asked for the email and the blocked IP address and at the completion of the procedure the IP will be delisted.
HOTMAIL.COM LIVE.COM MSN.COM OUTLOOK.COM
Microsoft does not have a blacklist verification system but does have a delisting procedure to use if your emails are rejected from their domains (hotmail.com, live.com, msn.com, outlook.com and other Microsoft domains), below the link:
Here too, follow the procedure by answering the questionnaire, the delisting is not immediate.
Microsoft also offers specific programs for reporting problems with the IPs used by the SMTP system:
Smart Network Data Services: https://postmaster.live.com/snds
SPF / DKIM
SPF is a protocol that allows the domain owner to declare which servers are authorized to send emails on their behalf, it is a very important parameter and also allows you to prevent hackers from sending emails on your behalf (spoofing) and declaring the authorized servers the reliability score is increased and consequently the sending quality of the emails.
The SPF record through a precise syntax lists authorized IP addresses and hostnames and indicates to the recipient the behavior to follow in case the emails arrive from a sender that does not respect the rule (soft-fail or hard-fail).
An excellent tool to be able to check your SPF / DKIM is the following