I haven't had any issues with either SMTP or IMAP on Fastmail. I've even used their IMAP server by hand with no issues. Here is the IMAP capability list (which

I haven't had any issues with either SMTP or IMAP on Fastmail. I've even used their IMAP server by hand with no issues. Here is the IMAP capability list (which shows protocol extensions supported) before logging in: * CAPABILITY IMAP4 IMAP4rev1 LITERAL+ ENABLE UIDPLUS SASL-IR NAMESPACE CONDSTORE SORT LIST-EXTENDED QRESYNC MOVE SPECIAL-USE CREATE-SPECIAL-USE IDLE AUTH=PLAIN and after: * CAPABILITY IMAP4rev1 LITERAL+ ID ENABLE ACL RIGHTS=kxten QUOTA MAILBOX-REFERRALS NAMESPACE UIDPLUS NO_ATOMIC_RENAME UNSELECT CHILDREN MULTIAPPEND BINARY CATENATE CONDSTORE ESEARCH SEARCH=FUZZY SORT SORT=MODSEQ SORT=DISPLAY SORT=UID THREAD=ORDEREDSUBJECT THREAD=REFERENCES THREAD=REFS ANNOTATE-EXPERIMENT-1 METADATA LIST-EXTENDED LIST-STATUS LIST-MYRIGHTS LIST-METADATA WITHIN QRESYNC SCAN XLIST XMOVE MOVE SPECIAL-USE CREATE-SPECIAL-USE DIGEST=SHA1 X-REPLICATION STATUS=SIZE OBJECTID SAVEDATE X-CREATEDMODSEQ XAPPLEPUSHSERVICE LOGINDISABLED XCONVERSATIONS COMPRESS=DEFLATE X-QUOTA=STORAGE X-QUOTA=MESSAGE X-QUOTA=X-ANNOTATION-STORAGE X-QUOTA=X-NUM-FOLDERS IDLE They only have the TLS ports open; the plain text services are disabled (no need for STARTTLS since that's insecure from MITM). They allow having a password different from the account password specifically for these services.