Problem with emails ending in spam

Hello everyone,
Our emails were working just fine for the past months, last week we finally were able to finish our costumer app + email invoicing.
The problem is that we sent over 2000 emails for invoices and some were sent to spam.
Which I don't understand why since before the emails were working just fine. Any advice? Is there a daily limit of emails to be sent? We are using ISPConfig for our email server.

Thank you,
Diogo Jesus

 

You have to ask that from your internet service provider. There may be limits.

ISPConfig is not a e-mail server. ISPConfig is a control panel. You are probably using Postfix as your e-mail server if you installed ISPConfig the usual way.
To find out why mails end up in SPAM folder, examine those mails. You maybe get return mail that shows why it was put to SPAM? And examine if you mail host is in black lists. See for example mxtoolbox.com

 

All our emails were sent. My concern is if google target as spam after sending around 1000 emails to their mailboxes.

I know, it's postfix I just didn't want to lose time with all the details. But yes it's postfix and was working great for the past months.

Our server is not blacklisted. But i'll try to figure out from the emails headers. Thank you

 

After some digging on our logs I found out that most of the emails sent to gmail were in queue (gmail only) Other emails providers were accepting it just fine. Also from the headers I couldn't find anything weird

 

That can happen. Check if you have deferred mails, using command

Code:

mailq

 

I was trying to find it out on google but couldn't find any link related to that information. Could I get a link about that? Thank you,

Thank you. There were few emails that were not sent and were hanging there

 

Thank you