To guarantee an email marketing campaign's success, you need to prepare before starting to send emails. Not doing so will land your email in spam or bounce it without reaching the subscriber mailbox.
Cleaning your mailing list of old and unusable email addresses is one of the most important things you should do. A bulk email verifier tool will clean and confirm each email address on your sending list.
Bulk email validation should stick to the following best practices:
Email address deduplication
As your mailing list grows, it may have the same email address appear more than once on your subscriber base. Some users use email aliases which point to the same mailbox. Keeping them on your mailing list will lead to duplicate messages sent to the same email address and negatively affect your sender's reputation and undesired customer feedback.
A mailing list may have email addresses with typos and syntax errors. Most common syntax errors are forbidden characters, misspelled domain names, leading or trailing spaces, etc. An email server will not be able to deliver an email to those addresses.
Mail server verification
The most crucial step in email verification is to check that a mailbox exists. Verify that a mail server can deliver to that address. An email verification tool will connect to the server and ping the mailbox.
Some servers' configuration limits or makes it impossible to validate an email address reliably using mailbox pinging.
A mail server will accept a message sent to any address, even if an email address does not exist. If an email address is invalid, a message will be delivered to a special catch-all mailbox or bounced later.
A server will temporarily reject a message and greylist a sending server for a short amount of time. This method helps in fighting spam, assuming that spammers usually do not send rejected messages later. At the same time, legitimate sending servers will try to redeliver a message.
Usually, a handshake between sending and receiving mail servers takes only a fraction of a second. Servers that apply tar pitting will deliberately delay communication. This approach also helps fighting spammers.