openssl return

$ openssl s_client -connect mail.dylanjcain.com:993
CONNECTED(000001B4)
---
Certificate chain
 0 s:C = DE, ST = NRW, L = Willich, O = mailcow, OU = mailcow, CN = mail.dylanjcain.com
   i:C = DE, ST = NRW, L = Willich, O = mailcow, OU = mailcow, CN = mail.dylanjcain.com
---
Server certificate
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
subject=C = DE, ST = NRW, L = Willich, O = mailcow, OU = mailcow, CN = mail.dylanjcain.com

issuer=C = DE, ST = NRW, L = Willich, O = mailcow, OU = mailcow, CN = mail.dylanjcain.com

---
No client certificate CA names sent
Peer signing digest: SHA256
Peer signature type: RSA-PSS
Server Temp Key: X25519, 253 bits
---
SSL handshake has read 2291 bytes and written 401 bytes
Verification error: self signed certificate
---
New, TLSv1.3, Cipher is TLS_AES_256_GCM_SHA384
Server public key is 4096 bit
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
Early data was not sent
Verify return code: 18 (self signed certificate)
---
* OK [CAPABILITY IMAP4rev1 SASL-IR LOGIN-REFERRALS ID ENABLE IDLE LITERAL+ AUTH=PLAIN AUTH=LOGIN] Dovecot ready.
---
Post-Handshake New Session Ticket arrived:
SSL-Session:
    Protocol  : TLSv1.3
    Cipher    : TLS_AES_256_GCM_SHA384
    Session-ID: 964FD2F033B167ADD32E1898F04ADD383543D5F904F053900139561CE6491FDA
    Session-ID-ctx:
    Resumption PSK: F1548C6639FB53EC52FF78F8A91EAB6A08475B70DE64827984CBC64C6AFA41FD3F8A275710253D402FF4AFAE4C6A6E01
    PSK identity: None
    PSK identity hint: None
    SRP username: None
    TLS session ticket lifetime hint: 7200 (seconds)
    TLS session ticket:
    0000 - 7d 56 1d cb 66 01 29 b8-a7 49 30 1b bf fc be 08   }V..f.)..I0.....
    0010 - be 9d 65 1a 2a d5 c6 00-8f 69 a9 ad 1f 4b a3 ce   ..e.*....i...K..

    Start Time: 1649847584
    Timeout   : 7200 (sec)
    Verify return code: 18 (self signed certificate)
    Extended master secret: no
    Max Early Data: 0
---
read R BLOCK
---
Post-Handshake New Session Ticket arrived:
SSL-Session:
    Protocol  : TLSv1.3
    Cipher    : TLS_AES_256_GCM_SHA384
    Session-ID: 755B7B3022E58F448C3F9076A844D70594FD4EA807E75526A73BA458DE27D68A
    Session-ID-ctx:
    Resumption PSK: 82D14DDF8ADB83C575465B8D9C3BA5EF91F7F3FA79E8518226044D0162C309CEE072C1CEC962BF874982519604994C62
    PSK identity: None
    PSK identity hint: None
    SRP username: None
    TLS session ticket lifetime hint: 7200 (seconds)
    TLS session ticket:
    0000 - b8 b5 c9 ed b9 b7 ee 9d-58 fc 39 ae 92 ff 15 56   ........X.9....V
    0010 - 9a e3 af ae 66 75 f6 e8-9f 01 b9 7b 5d 63 fd f1   ....fu.....{]c..

    Start Time: 1649847584
    Timeout   : 7200 (sec)
    Verify return code: 18 (self signed certificate)
    Extended master secret: no
    Max Early Data: 0
---
read R BLOCK
depth=0 C = DE, ST = NRW, L = Willich, O = mailcow, OU = mailcow, CN = mail.dylanjcain.com
verify error:num=18:self signed certificate
verify return:1
depth=0 C = DE, ST = NRW, L = Willich, O = mailcow, OU = mailcow, CN = mail.dylanjcain.com
verify return:1