You cannot see it directly on an invoice, but you can retrieve a list of invoices sent via mail via Reports - Queries.
So you can check:
- Open the menu: Reports - Queries:
- Click on new.
- Enter a description
- Paste text at the bottom of this mail in the box on the SQL tab
- At the top, click the checkmark to save
- Then click the execute SQL button
- Enter the journal, number and date (YYYY-MM-DD)
Select Dagboek, DocNr, CAST(DocDatum AS DATE) AS DocDatum , RekKlLev, K.Naam, DocVerzendDatum,
case when DocVerzendType=9 THEN ''
when DocVerzendType=0 THEN 'Printer'
when DocVerzendType=1 THEN 'Email'
when DocVerzendType=9 THEN 'Niet verzonden'
ELSE '' END AS Methode,
IFNULL(DocVerzendMail, '',DocVerzendMail) AS MailAdres
FROM FakHead f
LEFT JOIN Klanten k ON f.RekKlLev=k.Referte
WHERE Dagboek='{[Dagboek]}'
AND DocNr ={[Nummer]}
AND DocDatum = DATE '{[Factuurdatum_YYYY-MM-DD]}'