I have a server and the postfix client on it.

Since several days, I noticed a lot of processes running there. When checked, there are a lot of emails sent.

Here is an example from the mail log:

Aug 18 11:54:56 mem postfix/smtpd[9963]: connect from dslb-188-096-082-167.188.096.pools.vodafone-ip.de[188.96.82.167]
Aug 18 11:54:56 mem postfix/smtpd[9301]: connect from unknown[186.113.45.4]
Aug 18 11:54:56 mem postfix/smtpd[9963]: 525E7114012D: client=dslb-188-096-082-167.188.096.pools.vodafone-ip.de[188.96.82.167]
Aug 18 11:54:56 mem postfix/cleanup[9970]: 525E7114012D: message-id=<B55835C9027BFA9D16CCBB556DB2F48BB82DF004000480BA-db0c3ce8aa74446411898d0d2feb3001@email.filmforthoughtinc.com>
Aug 18 11:54:56 mem postfix/qmgr[2581]: 525E7114012D: from=<[email protected]>, size=10702, nrcpt=1 (queue active)
Aug 18 11:54:56 mem postfix/smtpd[9301]: EC52711401DC: client=unknown[186.113.45.4]
Aug 18 11:54:57 mem postfix/smtpd[9963]: disconnect from dslb-188-096-082-167.188.096.pools.vodafone-ip.de[188.96.82.167]
Aug 18 11:54:57 mem postfix/cleanup[8597]: EC52711401DC: message-id=<4C905D97606B436FE50C6F738DE014D9D84F2185BA815D81-1a4dbe6fc2bfcc8183f5faf901cfa15e@email.manguerasespecializadas.com>
Aug 18 11:54:57 mem postfix/smtp[9971]: 525E7114012D: to=<[email protected]>, relay=mail.mdpi.com[209.237.236.228]:25, delay=1.2, delays=0.55/0/0.45/0.16, dsn=5.1.1, status=bounced (host mail.mdpi.com[209.237.236.228] said: 550 5.1.1 <[email protected]>: Recipient address rejected: mdpi.com (in reply to RCPT TO command))
Aug 18 11:54:57 mem postfix/cleanup[10067]: 8B1E11140268: message-id=<[email protected]>
Aug 18 11:54:57 mem postfix/bounce[10001]: 525E7114012D: sender non-delivery notification: 8B1E11140268
Aug 18 11:54:57 mem postfix/qmgr[2581]: 8B1E11140268: from=<>, size=12693, nrcpt=1 (queue active)
Aug 18 11:54:57 mem postfix/qmgr[2581]: 525E7114012D: removed
Aug 18 11:54:57 mem postfix/qmgr[2581]: EC52711401DC: from=<[email protected]>, size=10978, nrcpt=1 (queue active)
Aug 18 11:54:57 mem postfix/smtp[10013]: connect to aspmx.l.google.com[2607:f8b0:400d:c03::1b]:25: Network is unreachable
Aug 18 11:54:57 mem postfix/smtpd[9301]: disconnect from unknown[186.113.45.4]
Aug 18 11:54:58 mem postfix/smtp[10013]: 8B1E11140268: to=<[email protected]>, relay=aspmx.l.google.com[74.125.22.26]:25, delay=0.5, delays=0.06/0/0.28/0.16, dsn=5.1.1, status=bounced (host aspmx.l.google.com[74.125.22.26] said: 550-5.1.1 The email account that you tried to reach does not exist. Please try 550-5.1.1 double-checking the recipient's email address for typos or 550-5.1.1 unnecessary spaces. Learn more at 550 5.1.1 http://support.google.com/mail/bin/answer.py?answer=6596 l7si24621420qad.26 - gsmtp (in reply to RCPT TO command))
Aug 18 11:54:58 mem postfix/qmgr[2581]: 8B1E11140268: removed
Aug 18 11:54:58 mem postfix/smtp[9971]: EC52711401DC: to=<[email protected]>, relay=mail.mdpi.com[209.237.236.228]:25, delay=1.2, delays=0.66/0/0.44/0.12, dsn=5.1.1, status=bounced (host mail.mdpi.com[209.237.236.228] said: 550 5.1.1 <[email protected]>: Recipient address rejected: mdpi.com (in reply to RCPT TO command))
Aug 18 11:54:58 mem postfix/cleanup[9970]: 414361140254: message-id=<[email protected]>
Aug 18 11:54:58 mem postfix/bounce[10001]: EC52711401DC: sender non-delivery notification: 414361140254
Aug 18 11:54:58 mem postfix/qmgr[2581]: 414361140254: from=<>, size=13057, nrcpt=1 (queue active)
Aug 18 11:54:58 mem postfix/qmgr[2581]: EC52711401DC: removed
Aug 18 11:55:01 mem postfix/smtp[10002]: 414361140254: to=<[email protected]>, relay=manguerasespecializadas.com[99.198.96.210]:25, delay=2.9, delays=0.04/0/2.1/0.84, dsn=2.0.0, status=sent (250 OK id=1XJPGs-0007BE-OI)
Aug 18 11:55:01 mem postfix/qmgr[2581]: 414361140254: removed

IS my server attacked, spammed? How to check that? Thank you.