(setq gnus-secondary-select-methods
'((nnimap "ustc"
(nnimap-address "mail.ustc.edu.cn")
(nnimap-server-port 993)
(nnimap-stream ssl)
(nnimap-inbox "INBOX")
(nnimap-authinfo-file "~/.authinfo.gpg"))))
(setq network-security-level 'high)
(setq gnutls-algorithm-priority
"SECURE192:+SECURE128:-VERS-ALL:+VERS-TLS1.2:+VERS-TLS1.3:%PROFILE_MEDIUM"
gnutls-min-prime-bits 2048
gnutl-verify-error t)
每次Group buffer进入inbox的时候emacs都会卡住， minibuffer里显示read 0k from mail.ustc.edu.cn就卡住了，而且CPU的一根核心会被拉到100%，如果不及时C-g甚至能把linux都卡死 
我试着用 gnutils-cli-debug，返回的结果似乎没啥问题（跟imap.qq.com的返回结果几乎一样）：
$:gnutls-cli-debug -V -p 993 mail.ustc.edu.cn
GnuTLS debug client 3.6.13
Checking mail.ustc.edu.cn:993
unknown protocol 'imaps'
whether the server accepts default record size (512 bytes)... yes
whether %ALLOW_SMALL_RECORDS is required... no
whether we need to disable TLS 1.2... no
whether we need to disable TLS 1.1... no
whether we need to disable TLS 1.0... no
whether %NO_EXTENSIONS is required... no
whether %COMPAT is required... no
for TLS 1.0 (RFC2246) support... yes
for TLS 1.0 (RFC2246) support with TLS 1.0 record version... skipped
for TLS 1.1 (RFC4346) support... yes
fallback from TLS 1.1 to... skipped
for TLS 1.2 (RFC5246) support... yes
for TLS 1.3 (RFC8446) support... no
for known TLS or SSL protocols support... yes
TLS1.2 neg fallback from TLS 1.6 to... failed (server requires fallback dance)
for inappropriate fallback (RFC7507) support... yes
for certificate information... saved in debug-certs.out
for certificate chain order... sorted
for trusted CAs... none
for safe renegotiation (RFC5746) support... yes
for Safe renegotiation support (SCSV)... skipped
for encrypt-then-MAC (RFC7366) support... no
for ext master secret (RFC7627) support... no
for heartbeat (RFC6520) support... yes
for version rollback bug in RSA PMS... dunno
for version rollback bug in Client Hello... no
whether the server ignores the RSA PMS version... no
whether small records (512 bytes) are tolerated on handshake... yes
whether cipher suites not in SSL 3.0 spec are accepted... yes
whether a bogus TLS record version in the client hello is accepted... yes
whether the server understands TLS closure alerts... partially
whether the server supports session resumption... yes
for anonymous authentication support... no
anonymous Diffie-Hellman group info... skipped
for RSA key exchange support... yes
for ephemeral Diffie-Hellman support... no
for RFC7919 Diffie-Hellman support... no
ephemeral Diffie-Hellman group info... skipped
for ephemeral EC Diffie-Hellman support... no
for VKO GOST-2012 (draft-smyshlyaev-tls12-gost-suites) support... no
for curve SECP256r1 (RFC4492)... no
for curve SECP384r1 (RFC4492)... no
for curve SECP521r1 (RFC4492)... no
for curve X25519 (RFC8422)... no
for AES-GCM cipher (RFC5288) support... yes
for AES-CCM cipher (RFC6655) support... no
for AES-CCM-8 cipher (RFC6655) support... no
for AES-CBC cipher (RFC3268) support... yes
for CAMELLIA-GCM cipher (RFC6367) support... no
for CAMELLIA-CBC cipher (RFC5932) support... yes
for 3DES-CBC cipher (RFC2246) support... yes
for ARCFOUR 128 cipher (RFC2246) support... yes
for CHACHA20-POLY1305 cipher (RFC7905) support... no
for GOST28147-CNT cipher (draft-smyshlyaev-tls12-gost-suites) support... no
for MD5 MAC support... yes
for SHA1 MAC support... yes
for SHA256 MAC support... yes
for GOST28147-IMIT MAC (draft-smyshlyaev-tls12-gost-suites) support... no
for max record size (RFC6066) support... no
for OCSP status response (RFC6066) support... no
Google上的类似问题基本上都是由于没有配置好gnutls导致的，但是我目前的配置，qq邮箱和outlook都可以，甚至mail.ustc.edu.cn的smtp发信也没问题，就是imap会导致卡死…
