unknown@invalid.invalid

We are currently evaluating em client to replace 25 accounts with the paid version. However we have one sticking point and that some of the Emails are coming into the inbox as unknown@invalid.invalid. They are pop3 accounts and have tried the solutions offered on here however at this point in time imap is not an option.

Any help would be greatly received.
 

Hello Lee,
could you please send me one such message as EML file to rust@emclient.com ?
Please add a link to this forum thread to the body of the message.

Regards,
Olivia

Hello Lee,
while very unfortunate, the issue seems to be with the specific sender/ this sender’s mail server.
In the Mail source of the EML you sent me the From contact is “From: =?ISO-8859-1?Q?Mercer=A0&=A0Hughes=A0MRCVS_[ME4306716702:-842484616]?= <correct mail address here>”
The incorrectly formated From name is stopping the address from being parsed - manually changing the incorrect test will repair the specific EMLs, but since the format is wrong, we cannot fix this.
Can you contact the senders to repair their mail format?

Regards,
Olivia