Question Being unsubscribed from MailChimp repeatedly

[Mike99]

Server operating system version

Ubuntu 20.04.6 LTS

Plesk version and microupdate number

18.0.55 Update #2

Customer with Plesk email hosting is being unsubscribed from MailChimp subscription repeatedly.

Email account is hosted on Plesk, customer wants to be subscribed, swear to not clicking unsubscribe, mail is not forwarded anywhere so only one person has access to the mailbox.

First we did not believe the client but after contacting MailChimp support multiple times and investigating, it seems that when this client receives email from mailing list that he wants to be subscribed to, something is repeatedly unsubscribing this client and clicking all the links in the email multiple times.

Can this be spam filter, spam checker or something checking links for the incoming email?

Anyone any ideas on how to investigate this issue or please share your experience from the past?

 

[Mike99]

UPDATE: Additional information, customer is using only the webmail to read emails, no other mail client at all, so buggy Outlook or mobile mail client is ruled out. This I can confirm from logs.

 

[Kaspar]

Do you have any additional email security related extensions installed on your server? Or are you just running Plesk with the default SpamAssassin setup?

It seems unlikely to me that a spam filter would cause this kind of behaviour. A more likely suspect would a browser plugin or some type of AV scanner used by your customer.

You could test this of course. Create your own free MailChimp account and a test mailbox on your server. Send a test mail from mailchimp to your test mailbox and see what happens next.

 

[mow]

Does the customer use a browser that has link prefetch enabled?
(this is a big security risk when it prefetches links from 3rd party hosts)