MailKit is an Open Source cross-platform .NET mail-client library that is based on MimeKit and optimized for mobile devices.

Features include:

• HTTP, Socks4, Socks4a and Socks5 proxy support.
• SASL Authentication via ANONYMOUS, CRAM-MD5, DIGEST-MD5, LOGIN, NTLM, OAUTHBEARER, PLAIN, SCRAM-SHA-1, SCRAM-SHA-256, SCRAM-SHA-512 and XOAUTH2.
• A fully-cancellable SmtpClient with support for STARTTLS, 8BITMIME, BINARYMIME, ENHANCEDSTATUSCODES, SIZE, DSN, PIPELINING and SMTPUTF8.
• A fully-cancellable Pop3Client with support for STLS, UIDL, APOP, PIPELINING, UTF8, and LANG.
• A fully-cancellable ImapClient with support for ACL, QUOTA, LITERAL+, IDLE, NAMESPACE, ID, CHILDREN, LOGINDISABLED, STARTTLS, MULTIAPPEND, UNSELECT, UIDPLUS, CONDSTORE, ESEARCH, SASL-IR, COMPRESS, WITHIN, ENABLE, QRESYNC, SORT, THREAD, ANNOTATE, LIST-EXTENDED, ESORT, METADATA / METADATA-SERVER, NOTIFY, FILTERS, LIST-STATUS, SORT=DISPLAY, SPECIAL-USE / CREATE-SPECIAL-USE, SEARCH=FUZZY, MOVE, UTF8=ACCEPT / UTF8=ONLY, LITERAL-, APPENDLIMIT, STATUS=SIZE, OBJECTID, REPLACE, SAVEDATE, XLIST, and X-GM-EXT1.
• Client-side sorting and threading of messages (the Ordinal Subject and the Jamie Zawinski threading algorithms are supported).
• Asynchronous versions of all methods that hit the network.
• S/MIME, OpenPGP, DKIM and ARC support via MimeKit.
• Microsoft TNEF support via MimeKit.

<PackageReference Include="MailKit" Version="4.5.0.1072" />

source https://www.myget.org/F/mimekit/api/v3/index.json

nuget MailKit  ~> 4.5.0.1072

Import-Module PowerShellGet
Register-PSRepository -Name "mimekit" -SourceLocation "https://www.myget.org/F/mimekit/api/v2"
Install-Module -Name "MailKit" -RequiredVersion "4.5.0.1072" -Repository "mimekit"