Why does a welcome email go to spam when other emails go to inbox for a known subscriber?

Email marketer from Litmus shares that poor list hygiene (e.g., sending to old or inactive email addresses) can damage your sending reputation, causing even welcome emails to known subscribers to land in the spam folder.

Email marketer from Reddit explains that low sending volume, especially when starting a new campaign, can cause welcome emails to be flagged until the sender builds a consistent and positive reputation.

Email marketer from StackExchange answers that if a subscriber has not recently engaged with previous emails, the welcome email may be treated with suspicion by mailbox providers and filtered accordingly.

Email marketer from Email on Acid answers that authentication protocols (SPF, DKIM, DMARC) not being properly set up for the sending domain can cause welcome emails to be flagged as spam, even for subscribers who generally receive your emails.

Email marketer from Email Marketing Forum shares that welcome emails from shared IPs are more likely to land in spam, especially if other users on the same IP are engaging in poor sending practices.

Email marketer from HubSpot shares that specific words or phrases (spam trigger words) within a welcome email can cause it to be filtered as spam, even if the sender is otherwise trusted by the recipient.

Email marketer from Mailjet shares that welcome emails may land in spam because they often contain generic content or triggers spam filters due to a lack of engagement history with the recipient.

Email marketer from ActiveCampaign shares that new IP addresses often need to be 'warmed up' to establish a sending reputation. Welcome emails sent from a new IP are more likely to be flagged as spam until the IP is trusted.

Email marketer from SendPulse explains that welcome emails frequently contain higher image-to-text ratios or promotional language, which can trigger spam filters, especially if the sender's domain is new or lacks a strong reputation.

Expert from Word to the Wise explains that welcome emails often contain more promotional content or incentives than regular emails, which can trigger spam filters due to perceived aggressiveness or pushiness.

Expert from Email Geeks explains that deliverability is about statistics, and it can't tell you much about an individual email or recipient beyond broad generalizations.

Expert from Word to the Wise explains that lack of recent engagement from the subscriber can cause the welcome email to be treated differently. Even if they were previously a good recipient, inactivity can negatively impact inbox placement.

Expert from Email Geeks explains that welcome emails are usually very different from other emails from the sender, as it's a different mail stream that people don't receive often or haven't interacted with much.

Expert from Email Geeks shares that the welcome email is a different mail stream, which may be perceived and treated differently from regular emails, even to a familiar recipient.

Documentation from Google Postmaster Tools explains that new senders often experience deliverability challenges because they haven't established a positive reputation with mailbox providers. Welcome emails, being the first interaction, are heavily scrutinized.

Documentation from DMARC.org explains that if a domain has a strict DMARC policy (e.g., p=reject), welcome emails failing authentication checks will be rejected or sent to spam, regardless of the recipient's prior engagement.

Documentation from Microsoft explains that even for known subscribers, their email client's safe sender list might not be immediately updated. The initial welcome email may be caught by filters before the address is fully trusted.

Documentation from RFC explains that if your domain's SPF (Sender Policy Framework) record is not properly configured, mailbox providers may flag welcome emails as potential phishing attempts, especially if the sending server isn't authorized.