SMTP
Simple Mail Transfer Protocol. The conversation between servers that delivers mail. Mailbox-level verification speaks a carefully limited version of this conversation without sending a message.
Simple Mail Transfer Protocol. The conversation between servers that delivers mail. Mailbox-level verification speaks a carefully limited version of this conversation without sending a message.
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Simple Mail Transfer Protocol. The conversation between servers that delivers mail. Mailbox-level verification speaks a carefully limited version of this conversation without sending a message.
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- Cold email & deliverability glossary
Plain-language definitions for the terms that come up in cold outreach and email deliverability: bounce rate, catch-all, SPF/DKIM/DMARC, sender reputation, and more.
- Bounce rate — cold email glossary
The share of sent emails a mail server refuses to deliver. A hard bounce means the mailbox does not exist; a soft bounce means it is temporarily unreachable.
- Hard bounce — cold email glossary
A permanent delivery failure: the mailbox does not exist, the domain does not accept mail, or the server has rejected the recipient for good. Hard bounces are the ones that wreck sender reputation.
- Soft bounce — cold email glossary
A temporary delivery failure: a full mailbox, a greylisting delay, or a receiving server that is down. Retrying can succeed; treating every soft bounce as a dead address thins a list for no reason.