Magento 2.2.5: system.log reads 'Invalid sender data' when attempting to send transactional e-mails.

[muckee]

@sashas777

I hadn't encountered this bug until I was attempting to test transactional e-mails, so I'm not sure whether the bug also affects the contact form or other mails, but I can confirm that the contact form is being sent successfully with a correct 'from' header.

Unfortunately, whenever I attempt to process an order, I see the same error in system.log. I am currently using the Mageplaza_Smtp module and so I can see a log of email info quite easily. Because transactional e-mails are not being sent, though, they are not logged... which means that I can't see what is being used in the 'from' header.

Is there any chance you could look at my server please? Or would you be able to tell me where in your code I can log the 'from' header to the console in order to see what is being used instead of my correct e-mail address?

Thanks!

[muckee]

P.S. I have disabled and uninstalled all of the modules which are known to affect SMTP/mailer modules.