Deleting attachments does not reduce file size


Senior Member
Outlook version
Outlook 2010 64 bit
Email Account
Hi guys. I am on Win10 and Office 365. I am on an IMAP system.
I am trying to reduce my mailbox size by (including other methods) deleting the attachments attached to emails with a large file size. I save the attachments to my PC and want to keep the emails but not their attachments. Opening the message and deleting attachment shows that it is gone but the file size remains the same. Closing/opening Outlook shows there is no attachment in the email but the file size has still not changed.
Is there a way to delete an attachment from an email and to reduce its size (without having to delete the whole email)?
Having searched this to no avail: no, I do not get warning messages. Everything works fine. Yes, I save the changes after removing the attachments.
Following your suggestion on this I will also need to know how I can remove the attachments from the emails that I have already done it on. Meaning I can see a large file size but now cannot see the attachments any more on numerous emails because I have theoretically deleted these attachments.
Thanks again for your input