Error when creating distribution lists in Bluewin Webmail

Environment: Bluewin Webmail (8.27.5, 8.27.59), Windows 10, browser Edge and FF (current versions, cache & cookies deleted).

Proceed:

Sent Open email -> 3-dot menu -> Save as distribution list

Distribution list -> Enter name -> Create list

Error message: “Invalid email address: ‘null’. Please correct the email address.”

The email addresses are valid, they have already been used.

A distribution list directly in the address book with “New distribution list” and then adding addresses works.

Can observations and errors be reported back directly?

Addendum: The error only occurs if one of the email addresses appearing in the email was previously imported into one of the address books (yourself, from another Swisscom account or through the Swisscom migration) or was created yourself. In most of the addresses transferred during migration, the email address is entered in the E-Mail 2 (Type=home) field. If the email address is moved to the E-Mail 1 field (Type=work), the error no longer occurs.