Email deliverability
Spam (junk mail) is a serious problem - about 45% of global email traffic is estimated to be unsolicited email. (Statista, Dec 2022)
To combat this menace, email providers are implementing ever more complex measures and tools.
The problem: a lot of the legitimate email is trapped in the battle with spam and cannot reach its recipient(s)
No matter if you are using a business email service (like Microsoft 365 or Google Workspace), your ISP/hosting provided email solution, or you host your own email server, you need to take measures to ensure mail deliverability.
Setting up SPF, DKIM and DMARC
Failing to properly configure Sender Protection Framework (SPF), DomainKeys Identified Mail (DKIM) and Domain-based Message Authentication, Reporting & Conformance (DMARC) will result in a message, similar to the following:
host gmail-smtp-in.l.google.com[74.125.133.27] said:
550-5.7.26 This mail is unauthenticated, which poses a security risk to the
550-5.7.26 sender and Gmail users, and has been blocked. The sender must
550-5.7.26 authenticate with at least one of SPF or DKIM. For this message,
550-5.7.26 DKIM checks did not pass and SPF check for [example.com] did
550-5.7.26 not pass with ip: [XXX.XXX.XXX.XXX]. The sender should visit
550-5.7.26 https://support.google.com/mail/answer/81126#authentication for
550 5.7.26 instructions on setting up authentication.
Get help setting up or troubleshooting SPF, DKIM and DMARC records for your domain.
Setting up reverse DNS (PTR) records
Reverse DNS (PTR) records are a mechanism for matching an IP address to a domain name. The absense of reverse DNS PTR record is a spam signal - if your PTR record does not exist, or does not match your mail server settings, some email servers would consider your mail as spam, while others would outright reject it.
Get help setting up a reverse DNS (PTR) record for your domain.
Repair a Bad Domain Reputation (Gmail)
If your domain has a bad domain rebutation, your messages will end up in Junk folder for Gmail recipients, or get blocked altogether, with a message like the following:
Action: failed
Status: 5.7.350
Diagnostic-Code: smtp;
550 5.7.350 Remote server returned message detected as spam
-> 550 5.7.1 Our system has detected that this;
message is likely suspicious due to the very low reputation of the;
sending domain. To best protect our users from spam, the message has;
been blocked. Please visit;
https://support.google.com/mail/answer/188131 for more information.
Remote-MTA: dns;
mx.google.com
Get help repairing your domain reputation status.
Your domain or IP address are blacklisted
Realtime Blacklist (RBL) or DNS-based blacklist (DNSBL) is a type of service, which hosts dynamic lists with domains and IP addresses of spammers. There are hundreds of RBLs / DNSBLs, which use different methods (most commonly honeypots - listing email addresses for spammers to discover and start to send emails to) to detect spamming servers or individual computers (usually infected with viruses) on the Internet.
Email providers use these lists to filter-out known spammers. If your server was blacklisted, you would have to take active measures to get delisted, things will not get better on their own.
Each RBL has its own procedure for listing and de-listing a server. Some have a dedicated URL for submitting a delisting request form, others would automatically delist your server after they have not received spam for a set period of time, while others require you to send an email asking for delisting and somebody to manually review your request.
Get help delisting your server from a RBL / DNSBL.