Can email signatures, especially via Exclaimer, cause SPF or DKIM failures and impact email delivery?

Email marketer from StackOverflow explains the challenges of email signature services altering email content, which can invalidate DKIM signatures. Suggesting using a service that signs the email after signature insertion or implementing DomainKeys Identified Mail (DKIM) signing after the signature service has processed the message.

Email marketer from Mailtrap.io shares that third-party email signatures can rewrite emails and cause authentication problems, potentially resulting in emails being marked as spam. Proper configuration of SPF and DKIM is crucial when using these services.

Email marketer from the EmailGeeks Forum reported issues with email deliverability after implementing a new company-wide email signature through a third-party service. They found that the signatures were altering the email content in a way that invalidated DKIM signatures. The solution was to adjust the settings in the third-party service to ensure DKIM signing occurred after the signature was applied.

Email marketer from DigitalMarketer explains that large image sizes in email signatures can lead to increased load times, contributing to poor user experiences. The author recommends optimizing image size to improve deliverability.

Email marketer from Email on Acid explains how incorrect handling of email signatures by third-party services can impact deliverability by causing SPF and DKIM failures. Suggests regularly monitoring authentication reports.

Email marketer from Litmus warns that overly complex or large email signatures can trigger spam filters. Suggests testing email deliverability with and without signatures to assess their impact.

Email marketer from GMass.co explains that overly large email signatures, especially those with embedded images, can increase email size, potentially triggering spam filters. They recommend optimizing signature size and using linked images instead of embedded ones.

Email marketer from Reddit shares an experience where implementing a company-wide email signature solution led to SPF failures and emails landing in spam folders. They resolved the issue by ensuring the signature service was properly authorized in their SPF record.

Expert from Email Geeks states that the ball is in IT’s court and there’s not really anything you can do without more detailed data on the delivery issues.

Expert from Email Geeks suggests that receiving issues are likely unrelated to Exclaimer Cloud.

Expert from Spamresource.com explains that forwarding can break SPF as it is a common cause of SPF failures when emails pass through multiple servers which are not authorised to send on behalf of the original domain.

Expert from Email Geeks suggests it could be an IT policy, such as blocking all base64 encoded content. He advises asking IT for a list of their policies.

Expert from Email Geeks explains “Exclaimer strips out the DKIM when it receives an email, but it is re-applied by Microsoft 365 after it has been processed by Exclaimer and before being sent to the recipient server.” and confirms Authentication looks fine and the problem is unlikely to be SPF or DKIM related.

Expert from Email Geeks explains that the email structure is a bit janky but that Microsoft is known for that. He mentions there are links to exclaimer.net in the email which are not whitelabeled, so if they're commonly used in unwanted email that could have an impact.

Expert from Word to the Wise explains that email signature services can alter email content, which can invalidate DKIM signatures if not handled correctly. Ensuring the signature service properly manages DKIM signing after signature insertion is crucial for maintaining deliverability.

Expert from Email Geeks explains that if Exclaimer is stripping DKIM before forwarding, the problem is you're publishing p=reject and you're telling recipients to throw away mail after the authentication is removed. She confirms that DMARC is passing.

Expert from Email Geeks explains that providing specific details like domains, IP addresses, rejection messages, and involved blocklists would increase the odds of receiving helpful advice.

Expert from Email Geeks explains the next step is probably to find out more about the delivery failures. If the mail was rejected, look at the rejection message. If it was delivered to spam, ask a friendly recipient to ask their admin why it was.

Documentation from DMARC.org highlights that using third-party services, including those that add email signatures, requires careful SPF configuration to ensure proper authentication. Failing to do so can result in DMARC failures and reduced deliverability.

Documentation from Exclaimer.com explains that when using a third-party email signature service like Exclaimer, emails are routed through their servers, potentially causing SPF failures because the email appears to originate from a different server than the domain's authorized sending sources. They recommend updating the SPF record to include Exclaimer's sending servers to resolve this issue.

Documentation from Microsoft.com explains that email forwarding can break DKIM signatures, especially if the forwarding server modifies the message content. This can lead to deliverability issues as the receiving server may fail to authenticate the email.

Documentation from RFC Editor (RFC 6376) explains that any modification to an email message after it has been signed with DKIM can invalidate the signature, leading to authentication failures. This includes changes made by email signature services.

Documentation from AuthSMTP provides guidelines on how email signatures can impact email deliverability, especially when third-party services are used. Proper SPF and DKIM configuration is necessary to prevent authentication failures. The email signatures can cause issues if they are not configured correctly in DNS records.