Email deliverability concerns reaching recipients’ inboxes. Acceptance by a receiving server does not by itself establish inbox placement. Google’s Gmail guidance covers sender authentication and sending practices, with requirements that vary by volume. It recommends SPF, DKIM and DMARC authentication for sending domains. Source: Mailchimp: Email deliverability Source: Google: Email sender guidelines

Check every system that sends for you

List the systems used for holiday campaigns, enquiries and booking messages. Ask the person managing the domain to confirm the authentication for each sender against the provider’s current guidance. This creates a clear record of which service is sending each kind of email.

Investigate the symptom before changing the message

Review rejection notices, spam complaints and test messages across several mailbox providers. Keep the sending system and date with each result. This helps the team distinguish a sending problem from a subject line or offer that needs a separate marketing test.

Written and updated by Travelgenix. Sources checked on 19 October 2026. Practical advice and examples are Travelgenix editorial guidance.