Unable to send email but i receive ok.

Hello, i receive emails quite fine but when i try to send i get a “Can’t send” in Rainloop.
Upon checking the logs i find the following, but i don’t know what the problem is.
Any help would be much appreciated…

Dec 12 00:23:18 server dovecot: imap-login: Login: user=webmaster@grhost.eu, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, mpid=12234, TLS, session=<Pbjk6XWZ/NF/AAAB>
Dec 12 00:23:18 server postfix/submission/smtpd[12235]: warning: cannot get RSA certificate from file “/etc/pki/dovecot/certs/dovecot.pem”: disabling TLS support
Dec 12 00:23:18 server postfix/submission/smtpd[12235]: warning: TLS library problem: error:02001002:system library:fopen:No such file or directory:…/crypto/bio/bss_file.c:288:fopen(’/etc/pki/dovecot/certs/dovecot.pem’,‘r’):
Dec 12 00:23:18 server postfix/submission/smtpd[12235]: warning: TLS library problem: error:20074002:BIO routines:file_ctrl:system lib:…/crypto/bio/bss_file.c:290:
Dec 12 00:23:18 server postfix/submission/smtpd[12235]: warning: TLS library problem: error:140DC002:SSL routines:use_certificate_chain_file:system lib:…/ssl/ssl_rsa.c:615:
Dec 12 00:23:18 server postfix/submission/smtpd[12235]: connect from localhost[127.0.0.1]
Dec 12 00:23:18 server postfix/cleanup[12196]: 289B05DC1D: message-id=20191211232318.289B05DC1D@server.example.com
Dec 12 00:23:18 server postfix/qmgr[6514]: 289B05DC1D: from=double-bounce@server.example.com, size=872, nrcpt=1 (queue active)
Dec 12 00:23:18 server postfix/submission/smtpd[12235]: disconnect from localhost[127.0.0.1] ehlo=1 starttls=0/1 quit=1 commands=2/3
Dec 12 00:23:18 server dovecot: imap(webmaster@grhost.eu)<12234><Pbjk6XWZ/NF/AAAB>: Logged out in=11 out=462 deleted=0 expunged=0 trashed=0 hdr_count=0 hdr_bytes=0 body_count=0 body_bytes=0
Dec 12 00:23:18 server postfix/smtp[12198]: 289B05DC1D: to=postmaster@server.example.com, orig_to=, relay=none, delay=0.02, delays=0.01/0/0.01/0, dsn=5.4.4, status=bounced (Host or domain name not found. Name service error for name=server.example.com type=AAAA: Host not found)
Dec 12 00:23:18 server postfix/bounce[12200]: warning: 289B05DC1D: undeliverable postmaster notification discarded
Dec 12 00:23:18 server postfix/qmgr[6514]: 289B05DC1D: removed
Dec 12 00:23:18 server dovecot: imap-login: Login: user=webmaster@grhost.eu, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, mpid=12237, TLS, session=<Vl3r6XWZAtJ/AAAB>
Dec 12 00:23:18 server dovecot: imap(webmaster@grhost.eu)<12237><Vl3r6XWZAtJ/AAAB>: Logged out in=96 out=1011 deleted=0 expunged=0 trashed=0 hdr_count=0 hdr_bytes=0 body_count=0 body_bytes=0

Any further update