12.0p ds.xml Mail tag <to> handling question

[Blama]

Hi Isomorphic,

we have a strange issue with mails sent to multiple recipient via <to>a@test.com, b@test2.com, c@test2.com</to> (v12.0p_2020-03-11).
It seems this perhaps results in three To: mail-headers and one provider we tested does not allow this (https://www.gmx.net/mail/senderguidelines/). Also in this case Office 365 has a problem validating DKIM signatures (while googlemail does not?!). All very strange.
Fortunately for us, we almost never have multiple recipients, and never for that provider, so after a big uproar, this is most likely a non-issue for us.

I tried SMTP mails with the JavaMail.jar you ship and sample code from here myself and could not provoke this issue. So I'm wondering what it might be.

Could you explain how you process the <mail><to>-tag content? How does the framework feed it to MimeMessage.setRecipients() (there are two overloads)? Is there any preprocessing done by your code?

Thank you & Best regards
Blama

[Isomorphic]

We use addRecipients() API (the one with Address[] as parameter), so the problem must be on the implementation side which seems to be incompatible with certain receiving servers.

[Blama]

Hi Isomorphic,

thank you. I could not reproduce in my simple testcase. Super strange, but not important to us. Perhaps it's solely Office 365's fault.

Best regards
Blama