One question, we are currently sending our emails manually to our deals via the email function and templates. After testing, these are logged in GMail and also in your activities as “sent”.
Problem: But they don’t arrive at the recipient 
Hi @KUhrig,
Can you share a bit more context? How do you know that they don’t arrive? Are you testing with your own email addresses as recipients? Have actual recipients given you that feedback?
One reason might be, generally, that the emails are caught by filters that are supposed to prevent spam. These filters can be triggered by HubSpot’s email tracking: Turn off one-to-one email tracking or attachment logging
Switching this off might solve the issue.
Best regards!
We tried it with our own private e-mail addresses. Have stored test contacts and tried the process. For some other customers, the mails seem to arrive, for a few not, but are marked “Sent”. In other words, I have to switch off tracking to guarantee that the mails arrive, is that correct?
Hi @KUhrig,
There is a good chance that’ll solve the issue but no, there is no guarantee.
Best regards
Hi, I know this answer is long after your original post, but I was able to resolve this by simply unchecking the “Do not send to unengaged contacts” right before sending. Seems like if HubSpot has no record of you sending to them before it just doesn’t go properly.