Receive email from my own email address with pdf file. Must be infected!?

I receive emails from my own email address with attached some pdf file. I have not opened the file obviously as the accompanying text it in Russian. How can anyone use my email address? And why doesn't AVG identify this threat?

Hi Fons,
Thank you for contacting AVG Community Forum. I see you are facing issues with the mallicious email from your own email address. I am sorry for the inconvenience. Could you please share us the screenshot of the page (https://support.avg.com/SupportArticleView?urlname=AVG-Create-screenshot) which shows safe the malicious email?
You can post the screenshot here in your topic. Click on Answer & then click on the Image [mountain symbol] & follow the instructions. Thanks in advance.

Hi Fons,
Thank you for the screenshot. I would like to suggest you to delete this email and reset your email account password. Also set up a 2-step verification. AVG Internet Security  monitor your incoming emails and prevent you from receiving infected emails, or emails with malicious attachments. Email protection is provided by different AVG features according your email client: If you use an email client, such as Microsoft Outlook or Mozilla Thunderbird, Email Shield automatically scans your emails. If you use a web based email client such as Gmail or AOL, Web Shield automatically protects you from malicious email content.
If AVG fails to intercept a malicious email, or you notice that you are not receiving certain emails, you may need to correct the port numbers defined in the AVG Geek settings area. Please refer the article for the instructions:
| AVG (https://support.avg.com/SupportArticleView?l=en&urlName=troubleshoot-avg-antivirus-email-protection&q=email+guardian&supportType=home)
I hope this helps. If still you are facing any issues, please feel to contact us anytime. Thank you!

User-added image

Hi Fons,
Thank you for contacting AVG Community Forum. I see you are facing issues with the mallicious email from your own email address. I am sorry for the inconvenience. Could you please share us the screenshot of the page (https://support.avg.com/SupportArticleView?urlname=AVG-Create-screenshot) which shows safe the malicious email?
You can post the screenshot here in your topic. Click on Answer & then click on the Image [mountain symbol] & follow the instructions. Thanks in advance.

I am afraid to open the email, to open the attached pdf file. Text is in Russian, the email address ladu@ladu6.ee is used by me, for our webshop.